How to fix a Canon MX850 printer

SOURCE: Install canon i350

Go to this site. You can download the drivers.

http://www.usa.canon.com/consumer/controller?act=DownloadIndexAct

SOURCE: I am re-installing my canon ip5200r printer...

http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=DownloadDetailTabAct&fcategoryid=357&modelid=11994

Click select OS and then select your version of windows then install what pops up under drivers. This is your backup if the cd doesn't work

SOURCE: printer canon pixma mp190 installed need to chage to english

Since you have your printer pre-installed in Arabic, your best option is to get the english version of your printer driver and re-install it.
when you get to the link i will leave you with. download the file with this name:
mp190svst100ej.exe

http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&tabact=DownloadDetailTabAct&fcategoryid=334&modelid=16981

SOURCE: how to install canon printer MP140 without a disk

You can download the drivers and software for your printer from CANON:
http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=238&modelid=15294

Click on the "Drivers and Downloads" tab and then select you OS.

SOURCE: printer won't turn on ( mx850 )

I believe the fix is to disconnect power cord for an hour or so.
This is truly maddening... it's a bug in the design of their power supply.  It's happened to me three times in the past few months.
The first time it happened, I haplessly stumbled onto the solution wisdos mentioned (unplugging it for a while) without realizing it.  I thought it just started working for no apparent reason.
The second time I tried all sorts of tricks (not remembering the fact that I'd disconnected the power for a period), spoke with Canon support several times and finally had to agree to have them send me a replacement printer.
I'll skip the part about not being able to get the old printer's print head and inks out to put in the new one because it wouldn't budge without the power being on.
Now, with second printer and a five-second power failure, the same deal... won't turn on.  This time I pulled the power cord from the printer and let it sit for a few hours.  Plugged it back in and it came on.  
The maddening thing is that Canon support didn't want to escalate this to someone who might understand the power supply and diagnose the problem properly... their solution was to send out a new printer.  What a waste of time, money, and effort.