Stopped playing AVI

I have been using the WD box successfully for some months and I had a PC as a gateway with Vista Home Premium, 1tb drive connected via USB shared with Everyone read access, no Guest Account, no passwords. I changed the gateway PC to another with Visa Home Basic and set all configuration the same as before. Now I cannot access  the media files. When I browse to the Network Share I can see the folders but each time I try to open I get a message “Folder contains no Media Files” same if I browse to the external 1tb drive. All the files are stored as .avi. I took a new DVD and converted it to .avi and saved it to the external drive and I can see/play it fine. I re-ripped one there before does not recognise nor play. I can also browse to the folder direct and can see the file nnn.avi when I select it tells me it is an incorrect media type. Although again the once new ripped is OK. Bizarre, any ideas? 

It might be just a simple error in the connection did it just happen once or is it still on going?

First  step to take would be to reset the unit.

To reset the WDTV physically hold down the reset button on the side where the USB port is for 4 seconds and release

Another firmware update was released today, you could try and see if it helps. Try a factory reset from settings> system> reset to factory defaults as well.

Its been consistent not working since the last upgrade, restarted and factory default twice, will try the latest to version see. thanks

Upgraded to latest firmware, no change at all. I am running out of ideas and am now looking to buy anoher device as I cant waste hours trying to resolve this seemingly simple issue. BTW if I put the file on a flash drive and insert direct to the WDTVLive it works fine, just cant recognise it when on a remote drive.