Windows 7: file browsing in media center

hi all

hope you can help

Weird problem started few days ago

I have few folder in my video section.

When I browse it either works for few seconds or allows me to go up in folders and down ... then i leave it for a while... minute or so... and when I go down a folder and up again.. I just see the hours glass (circle) and no files...

any ideas... i have resored to last restore point.. updated drivers... updated codec

no result

thanks