JPG files from v3M on Sprint won't work on PC

My grandmother has a Motorola Razr v3M through her wireless carrier, Sprint. When we take pictures on the phone and save them to the memory card, everything seems to be working fine. We can view the pictures in the phone, and when we plug the memory card with adapter into the computer, we can see the file names. But when we try to preview or open the jpeg image files on the computer, we get an error message "An unknown error occurred while accessing (insert file name here)".

My concern is that Sprint did something to the phone because they want you to use THEIR image uploading service, which costs a monthly fee, and so they are having the images saved in some odd jpg format that only works with their program. But the Sprint people -AND- the Motorola people both deny this is the case. Please advise what the problem is... is this a memory card issue, a phone issue, a carrier issue, WHAT? Please reply as soon as possible.

Thank you,

Robert Koehler