PC communication with MP3 player lost

I apologize in advance as this may get a little wordy.
I started out with a Dell DJ the first time I used it, it worked fine, I managed to load roughly 200 songs. Shortly after that the device stopped communicating with my computer or vice versa not sure which. I talked to tech support with Dell did a whole bunch of things such as firmware updates, reloading software, reformatting, nothing worked. They sent me new device, again same thing, started out working then just stopped. So after the third attempt, I basically ate the restock fee and forgot about MP3 for awhile.

I now have an IRiver H20, I got for Christmas. I managed to load 700 songs into it, but now I'm having the exact same problem as I did with the Dell DJ. The mp3 player and my PC are no longer communicating. Windows recognizes that there is a device, and when I look at it in the device manager it says its working. However none of my media player software can detect it. (I have Yahoo Music unlimited, Mindows Media Player 10 and Realplayer 10)

I tried different USB ports, but if windows knows the device is there that doesn't seem like a USB problem and with this exact same thing happening with two completely different brands of device, it doesn't seem like it would be a problem with the player.

I also plugged the IRiver into my husband's PC and his media program recognized the device, though I'm not sure if it will continue to do so, as this happened with the Dell DJs as well and they lost communication with his PC after the first also.

Any ideas what may be the problem? Please help.