Streaming video clips from home network is touch and go

I have a wireless USB nic on my WD plus and I have it networked to a Windows XP box which has a share folder containing 300 video clips.  They are all various formats: flv, wmv, avi, mp4, etc.

So when i turn on my WD player I go to Video > Network Share > Fileserver >

and the files SOMETIMES show up.  All 300 of them.  And most of them play depending on the format.

But SOMETIMES, it says Network Share not available or something like that and I have to go to  Video > Media Server > Fileserver >

and then only 28 of the files show up and none of them play. 

I don’t understand what is happening.  It’s a 50/50 chance that I’ll get access to all my files.   Has anyone experienced this?

UPDATE:

I had a Windows XP Laptop which was also sharing files off the fileserver.  I powered it down last night and suddenly I was able to use Network Share instead of Media Server on the WD TV Live Plus.

Why is this happening?  When the laptop is on and I try to use the Network Share on the WD Tv live it says “No files in the current folder”.

Anyway, thanks for any guesses.