I have just downloadet and installed iTunes 7.5
Erased the old restore iPhone 1.1.1 ipsw file and asked it to restore my phone.
It downloadet the "old" ipsw file and restored the phone fine.
Jailbreak and so on went fine and it is still at v1.1.1
I have also sync fine with iTunes (outlook contact, images, video, music and so on)