It's possible that there was some kind of Chessbase Light ini file remaining even after uninstalling. I'd try uninstalling the program again, then looking for any ini files that were left behind.
a little help with chessbase light?

Oh my! I'm almost afraid to say anything for fear that I'll give you just enough information to be dangerous.
If you have any other Chessbase software on your PC other than Chessbase Light, be very careful. You might accidently delete files related to the other Chessbase software.
haha i don't, at least nothing important. i just downloaded it yesterday so i could run the tactics problems based off motif.

The exact file names and location will depend on whether you downloaded CB Lite 2007 or 2009, and which operating system you have. My CB Lite ini files for Win7 are located in my "C:\Users\<your name here>\AppData\Local\ChessBase" folder. If you have non-Win7, the folder locations will be different.
The ini files are configuration files with file extensions of ini. I think these ini files are sometimes left behind because Chessbase thinks you might want to reinstall a newer version and keep your old settings.
I'm hoping someone on here can help me. I downloaded CB lite so that i could run chessville's 1001 tactical problems, and when i first started running them it would answer for black when i made a move, and it wouldn't let me make any move but the right one. Idk if i pressed something or what but it stopped doing that. I uninstalled and redownloaded but its still stuck in this mode where it lets me make any move i want. Does anyone know how to get this running like a tactics trainer again?