Water will not pass through....

Brand of coffee maker? Could need cleaning with vinegar run through. Most have a clean feature but run with just 1/2 water and vinegar several times.

It may need de-scaling. When my Keurig did what yours is doing, I filled the reservoir 3/4 way with white vinegar, and ran the machine repeatedly until it all passed through. I then re-used that vinegar and did the whole pass through 3 more times. that cleared it up. Did that 9 months ago. Use: 6 cups/day.
One other source of this problem are the metal pieces that punctures the top and bottom of the K-cup. Coffee grinds can find their way in there, and can be cleaned out with a paper clip or mini-pipe cleaner. But clogging of the bottom puncturer usually results in overflow, unless the top is also blocked.
Good Luck

In an empty machine,(no coffee, no filter), pour in a 50-50 mixture of water and white vinegar. Allow the machine to start brewing and when a cup or so has run through, stop the brewing process and let it sit for an hour or two. This should dissolve some of calcium buildup in the machine and allow it to complete a full cycle. May have to do this a couple of times to fully clean out the mineral buildup. After cleaning, run a pot of clear water through to rinse out the remaining vinegar.

How old and have your ran vinegar water mixture to clean teh coffee maker? I woould run 1 part vinegar to one part water to clean coffee makers 2 -3 times a year. Here's a vinegar cleaning link.

http://ezinearticles.com/?How-To-Clean-A-Coffee-Maker&id=57769

hi there! Try to use a filter for your water (and not tap water)! Here in France we call it a Brita! it filters out scale and other unwanted substances! And if possible do not use vinegar to clean your Gaggia but a professional cleaner/de-scaler! go to joegloe homepage!

DO NOT USE THAT MUCH VINEGAR! Put a tiny bit of vinegar in the carafe and fill carafe the rest of the way with water. Run that vinegar/water through machine. Using another container, fill machine with plain water and run that through. Repeat until the vinegar taste is gone. If you do not run lots of plain water through the machine after, your coffee will taste like...um...disgusting! Also, use a spell-checker before improving this posting.
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To clean hard water deposits from a coffee maker use distilled white vinegar. You may need to use as much as a gallon if the scale buildup is really bad. Fill clean coffee pot one half full of vinegar and run through machine as if making coffee. Repeat this process several times using fresh vinegar until it comes out clear. Do this once a week and your maker will work much better. **************
Use citric acid or LEMON JUICE CONCENTRATE instead of vinegar. It cleans just as well but doesn't leave the funky odor that vinegar does. You can run enough water to get rid of the vinegar taste, but the odor will linger for days or weeks. Much better to use lemon juice concentrate (no pulp!!) or one of the commercial products like the one available from Starbucks.

Try cleaning it with white vinegar. Put in one cup with a potful of water, and let it soak. To get more cleaning, pour the water/vinegar through again, hot. Put in a coffee filter to catch/strain the debris, and you will be able to see if it's helping. When you're through cleaning, pass fresh water through the machine by potfuls, until no traces of vinegar can be detected.
Best regards, --W/D--

Suggestion was Descaling the Coffee Maker from KitchenAid Phoebe (I'm guessing customer support)

http://kitchenaidconversations.com/forums/topic.asp?TOPIC_ID=14441&SearchTerms=err+2
Cleaning scale from coffee maker DO NOT USE THAT MUCH VINEGAR! Put a tiny bit of vinegar in the carafe and fill carafe the rest of the way with water. Run that vinegar/water through machine. Using another container, fill machine with plain water and run that through. Repeat until the vinegar taste is gone. If you do not run lots of plain water through the machine after, your coffee will taste like...um...disgusting! Also, use a spell-checker before improving this posting. 

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To clean hard water deposits from a coffee maker use distilled white vinager. You may need to use as much as a gallon if the scale buildup is really bad. Fill clean coffee pot one half full of vinager and run through machine as if making coffee. Repeat this process several times using fresh vinager until it comes out clear. Do this once a week and your maker will work much better. 
Thanks.

Suggestion was Descaling the Coffee Maker from KitchenAid Phoebe (I'm guessing customer support)

http://kitchenaidconversations.com/forums/topic.asp?TOPIC_ID=14441&SearchTerms=err+2

Cleaning scale from coffee maker DO NOT USE THAT MUCH VINEGAR! Put a tiny bit of vinegar in the carafe and fill carafe the rest of the way with water. Run that vinegar/water through machine. Using another container, fill machine with plain water and run that through. Repeat until the vinegar taste is gone. If you do not run lots of plain water through the machine after, your coffee will taste like...um...disgusting!
**************
To clean hard water deposits from a coffeemaker use distilled white vinager. You may need to use as much as a gallon if the scale buildup is really bad. Fill clean coffee pot one half full of vinager and run through machine as if making coffee. Repeat this process several times using fresh vinager until it comes out clear. Do this once a week and your maker will work much better.

Suggestion was Descaling the Coffee Maker from KitchenAid Phoebe (I'm guessing customer support)

http://kitchenaidconversations.com/forums/topic.asp?TOPIC_ID=14441&SearchTerms=err+2

Cleaning scale from coffee maker DO NOT USE THAT MUCH VINEGAR!Put a tiny bit of vinegar in the carafe and fill carafe the rest of theway with water. Run that vinegar/water through machine. Using anothercontainer, fill machine with plain water and run that through. Repeatuntil the vinegar taste is gone. If you do not run lots of plain waterthrough the machine after, your coffee will tastelike...um...disgusting!
**************
To clean hard water deposits from acoffeemaker use distilled white vinegar. You may need to use as much asa gallon if the scale buildup is really bad. Fill clean coffee potone half full of vinegar and run through machine as if makingcoffee. Repeat this process several times using fresh vinegar until itcomes out clear. Do this once a week and your maker will work muchbetter.