picture problems with canon a640

so i had a one gig memory card which took about 170 pics per card. Then I found that my landbound camera had an eight gig card. so sneakily, i switched them out and formatted the 8g to my camera. i discovered shortly that the 8gig card kept taking odd pictures and having card read errors on the camera. so i switched back to the 1gig card and formatted it back. all went well until last night's pictures. can someone help me figure out what the heck is going on? I've only been taking pictures for about six weeks, so am a complete beginner at this.

Probably bad news, looks like either the card or the camera have developed problems.

Try reformatting the 1GB card in the camera, and if that does not work borrow a 3rd card from someone else to try.

If none of that works then it's probably a camera problem, so look in the manual and find out how to do a complete "reset" on the camera.