Signed MIDlets on the 6600 
Well with firmware 3.42.1 there was no chance of getting signed midlets to work. But now my firmware version is 4.09.1 and it's still not working.
I saw some success storys on the Forum Nokia discussion forum. Even with self-signed, user installed certificates.
But for me none of the solutions worked. Even some officially signed midlets downloaded from the internet don't install.
Midlet signing is from hell!
It might be the problem that I previously had firmware 3.42.1 on it. I'll make a phone backup and try a hard reset to see if it still won't install the signed midlets.