Hi, I had the same issue (I think). Had up & downgraded a few times and ended up with 1.1.1 but installer.app wasn;t allowing me to install 1.1.1 apps as it kept saying my formware wasn't 1.1.1 , funny thing is it also didn;t alow me to install 1.0.2 apps either.
What I ended up doing is Option+Restore (Shift+Restore on Windows) via iTunes and selected the 1.1.1 firmware again, after restore I did the jailbreakme.com trick to get WIfI and activate/unlock (
http://iphone.unlock.no/ )
Working like a charm again... pheew, i'll be staying away from 1.1.2 for a while.