Try disabling Vista "User Account Control" UAC and see if it makes a difference.... Just remember that by disabling UAC you are lowering your PC's security so you might not want to leave it off...
As a side note, I have been using Vista for about 6months...this is how I run it without problems....but please remember that my PC is only used for MediaPortal so security is not that important to me..
1) I log on using the "Administrator" account....you will have to enable it first...
2) I run Vista without a Firewall or an Antivirus.....
3) I have disabled UAC....
4) I run MediaPortal V1.0 as released...
5) I use ATI Avivo codec for TV.....
6) I use ATI CCC v8.12, because v9.1 causes intermittent crashes in MediaPortal.
I have finally gotten it to work properly and now it is staying working. You have seemed to be right. Although it was not just the password that screwed up MediaPortal and it's permissions. Anything I installed after I installed MP seemed to be making it go bad.
ffdshow seemed to make it stop working as well as the password as well as vlc media player.
Merely uninstalling these programs does not fix the problem, I had to format my HDD 3 times and reinstall Vista just so I could get it working. This does seem to be a major flaw in an otherwise superb program.
Hopefully this issue can be rectified in future updates and releases.
I would like to thank Paranoid Delusion and geov for their help!
I can not believe how frustrating this is. It seems as though my theory as stated above is false.
I am now getting the same error "Connection to TV Service is Lost".
All I did this time (in between it working.. and now not) was connect remotely and extract some files using WinRAR. This couldn't have messed with any permissions.