Vista - media center freezing the system when browsing library

Hello, I have a brand new Vista x64 HTPC which I have set as part of my wireless network.
an XP machine on the network has several shared folders with all my media on it (mostly XVID videos).
I have pointed WMP to these folders as well as the media center.
when attempting to browse the movie library the system has great difficulty generating the thumbnails and lock up after a while (timing before lockup is not consistent).
all my movies have pictures using the same file name located into the same folder so the media center should not have to go through the movie to generate the thumbnails; and the thumbnails displayed are consistent with the pictures located on the shared folder.
this happen even on folders containing less than 10 items.
I can successfully play the movies in XVID and DIVX format within Vista media center and never had any issue using MCE 2005 or mediaportal.
WMP also plays the movies fine and does not seem to have any issue with generating thumbnails (even though it insist on generating its own.).
removing the firewall did not help (I had to try).

I am new to vista, is there a log file that would indicate me what is locking the machine?

any help would be appreciated.

thank you

---------edit------------

the problem seems to be broader that formerly envisioned. I had the system locking while using the Netflix plugin and playing chess from within the media center.
I also had it to freeze once while using the Netflix player within IE.
I updated the BIOS to the latest version to no avail.
I will check the RAM and post back.

thank you