Classic os4 freezes on Iprefs

[amiga4001]

I was running os4 nicely on my amiga4000 unitl the last shutdown and restart this afternoon on a computermeeting.
Now it won't boot fully up anymore.
It boots until first reset and then boots up even further for quite a while and the black screen and nada.
I played around in startupsequence to try to get it to boot.
If I disable Iprefs it boots up ok with aga screen.
i can even test my voodoo3 card which then gives me a nice test picture..no problem.
But when I click use it just goes back to the aga screen nothing else.
Strange..voodoo3 card works ok in os3.9.
Bus is a mediator4000 and it all worked like a charm before.

[amiga4001]

I tried removing pci cards to no avail pushing them etc..
I deleted sreenmode.prefs same problem.
I saved to aga screenmode same problem.
Only time it boots till aga screenmode is whem I ;Iprefs.
But then I can't use any other screenmode then the standard 640*256.
I can use all testscreens but when I want to use a screenmode be it voodoo or aga higher res it just does nothing.
So don't know now..voodoo card seems to be ok hence the testscreen is ok and so is the ppc it seems as it boots up ok till the end.
Any more suggestions?