Compaq Presario C571NR Laptop
Default OS: WIndows Vista
Current OS(s): Windows XP, Ubuntu Linux Karmic Koala
Intel Pentium Dual Core, 1.73 Ghz (x 2)
Intel Graphics (Not sure on this, because i have absolutely nothing that gives me much detail, All I know is it IS intel)
1.5 Gb Ram
88 GB Hard drive (2 partitions, 1 linux 1 windows)
Screen Res: 1280 x 800
I strongly recommend, in your case, upgrading to Lucid Lynx (10.04). I had insane problems of all sorts with Karmic and Windows 7 drivers and Java and the like, but everything works amazingly well in Lucid.
If you can't, for some reason, update to Lucid, then I'd start by looking for memory errors, or restoring your computer to an earlier pre-update backup.