I've got at good one for you guys, cannot install .cab files

[Unknown Zone]

try to format the card.....since it sounds corrupted....maybe you can save it...but I would looking for a backup card.

[Raging Idiot]

well the remaining options are now obvious...
Try your friends card... if it works then reformat your corrupt card, if it doesn't then return/exchange your phone if possible.
And if turns out that you need a new card, expect to pay no more than $27 for 4gb and $80 for 8gb (both include shipping). Just found these deals here recently.

[cyberhippie]

thanks for the help guys! It was the SD card, I was able to get my stuff off of the card and format it! Works just fine now.