Memory card error

First, remove the card, and look in the slot for any bent flash card pins. If you see any, don't fret, it's possible that you can fix this yourself. See this article on how to unbend flash card pins.

But if no pent pins are seen, then the camera's clock battery has worn out, and is likely causing this problem. Unfortunately this battery is internal to the camera. But Canon will fix this for you (for the S400 only) for free, with free shipping. Please see the Canon advisory for your camera here.

Canon has recognized that the IXUS400\S400 camera had two manufacturing defects. One is a memory card error and the other is the CCD image sensor which can cause the LCD screen to act dysfunctional. Contact Canon. They will fix these issues for free. Even if the camera is out of factory warranty.

Canon had manufacturing issues regarding memory errors and also the CCD. They will fix this free of charge. Even if the camera is out of factory warranty. Contact Canon. They were very helpful and fixed the same issues on my S400

The internal BIOS battery has run down and is causing this error. Don't attempt to fix this yourself. Canon will fix this for you for free, with free shipping, regardless of your camera's warranty status. See and print out the following advisory:

http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=223&modelid=8777&keycode=2112&id=27465

This is a known issue.  Check out the Canon Support site: http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=223&modelid=8777&keycode=2112&id=27465

When a canon S400 displays a memory card error this means that it has experienced an anomaly. This means that you have to reformat the memory card. You can do this via the menu. Make sure that you backup the pictures on it using a CF card reader on your computer

The clock button battery inside the camera has expired. Canon will fix this for free (or if you want, will send you a replacement battery with instructions on changing it out). Read the following recall advisory, then contact Canon at 1-800-OK-CANON:

http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=223&modelid=8777&keycode=2112&id=27465

On the old Powershot S400, this error was caused by a dead internal "clock" button battery. Fixing it required simply replacing the battery. But before you attempt to do that, would first suggest trying a different memory card.

Hi momincali - I posted a solution for someone that seemed to have the same problem as you. If you didn't see it, this is what I wrote:

I had the same problem on my PowerShot S400 as well as I couldn't reformat the compact flash when using the feature on the camera. The solution that worked for me was reseating a small battery (about the size of a watch battery) in side the camera. To get to it you have to take the case apart.
I found this solution by googling and typing:
powershot S400 E50 error
I'm not sure if this site will allow me to add the web link - but this link had a picture of the camera and where the battery is located.
http://www.pinoyhack.com/2006/09/14/canon-powershot-s400-fix/

I decided to try it, since I figured I had nothing to loose, becaues otherwise I'd be looking for buying a new camera. To my surprise it fixed my problem, but I do not know if this is a permanent fix. If you do try this - take note of where each of the screws come from. There were 4 different size screws around the case.

There seem to be a lot of complaints about this problem though.

Good luck.

Solution:
1 set date to 31-12-2030 23h59 and switch camera off.
2 wait two minutes, day will be 01-01-2003 and camera asks you to set the date
3 take away memory card
4 set the date to today
5 insert memory card again
Now your error should be solved.
Sucess, Jonny