Same issue here. Ubuntu 9.10 Karmic. I watched a two hour movie with it, then played around with the menus for about five minutes, then it crashed. Now it crashes about a minute or so after loading. Unusable at this point...
Boxee BETA (always the latest)
HTPC - ASRock micro-ATX w/ NVidia 8200 onboard graphics (VDPAU) (AMD Athlon2 X2 2.9Ghz dual-core, 2GB RAM, gigabit LAN), bluetooth mouse/keyboard combo, Microsoft MCE IR remote
Linux Mint 9 Isadora 32-bit (Ubuntu 10.04), VGA-out, Optical Audio-out
Home-Server - Old-ass Athlon single-core system w/ 512MB RAM, gigabit LAN, 1TB external HD
Ubuntu 9.10 32-bit server edition, SABnazd, Episode Butler, MediaTomb, Samba, NFS