I am experiencing similar problems that Tommy is, my situation is somewhat different tho..
Whereas Tommy was using RC2 i'm using RC3, we both have the same tv card tho. I have been using RC2 for about a month or so and it was working fine, when I saw that the new RC3 was available I wanted to give that a try instead tho obviously.
After uninstalling RC2 and rebooting I also made a manual search thru the registry for any mediaportal entries and deleted all there was. Then I installed RC3, and before doing anything else extracted mediaportal-cvs-03-26-2006--01-13.rar into the MP folder and ran start.bat.
When I start MediaPortal.exe it opens the initial configuration wizard. No problems until i get to the [4/10] screen which is the scan for media one. If i start a scan and shortly after stop the scan mediaportal crashes without any error message. The very same thing happens if i skip the scanning and just press next to get to the 5th screen.
From what I can tell its SQLite related, and if im correct this wizard is supposed to create the databases but for some reason fails to do so and crashes.
I have prepared some logs which should come in handy at:
http://gaah.mine.nu/mp/
Any help appreciated!