Is that the only problem with the install? If not, you might try installing again sooner rather than later.
If yes, then try making a new user account, then logging into that account. If the problem doesn't affect the new user account, log back into the affected account and delete these:
Home > Library > Preferences > com.apple.screensaver.plist
Home > Library > Preferences > com.apple.systempreferences.plist
Then logout and log back in again.
I recently installed Snow Leopard on a first gen Core Solo Mini with 2 gigs of RAM, and migrated a whole account data from another computer running Lion.
You can't do this, Apple changed things in Lion especially in the hidden Users/Library, can't use Lion OS X files in Snow Leopard
You will need to manually copy your data out of the migrated from Lion user account folders that contain anything Music, Pictures, Movies etc., (except Library) off the machine to a regular storage drive.
Then your going to need to create another Admin user (if you don't have one already) log into it and delete the migrated from Lion user account, reboot, then recreate the same named user account, this will give you a 10.6 version of the Users/Library again, no Lion taint.
Then log into it and return files, but not the iPhoto Library or the iTunes folder, you will need to first get the orignal pictures and music out and reimport them into the 10.6 versions of these programs.
To get the orignal photo's out of the 10.7 iPhoto Library, right or control click on the 10.7 iPhoto Library and "show package contents" inside is a Originals folder, move that out and open 10.6 iPhoto and import that folder of pictures, they will go into the 10.6 iPhoto Library in the Pictures folder automatically.
In the 10.7 iTunes folder there is another inside folder that just contains your music etc. copy that out and import into 10.6 version of iTunes, you music will then be imported into the 10.6 version of the iTunes Music folder, your 10.7 playlists will be gone unfortunatly.
That's all I can help you with there, but the same tactic must be played for any other software that was tainted by Lion verisions.
What your doing basically is "reverting to Snow Leopard" Apple doesn't expect people to do this when they employed the migration assistant/ TimeMachine system, it's all forward and no reverse.
Create a new TM drive on the 10.6 system
Read this here, it's basically what your doing, reverting from 10.7 to 10.6, but your using another machine with 10.6 installed already.
Read this here, bootable clones are superior to TimeMachine's limitations.