I have the same problem with my N900 and Nokia Ck-300 car kit. I had this problem before and after PR1.2. Has anyone found a solution please?

The phone freezes for anything up to a minute when selecting any applications. Then, usually the application will start.
When I make calls I can not hear the person on the other end (and they cant hear me).
I get "Unable to play media. Audio in use by another application." when trying to play music.

Restarting solves the problem.

I spoke to Nokia support and after I told them that I did a fresh install of PR1.2 (rather than an upgrade) using Flasher they would not give any further help until I used Nokia PC Suite to reinstall PR1.2. After doing just that Nokia suggested returning the N900 under warranty.

I dont really want to do this because its a load of hassle and I think that the same problem will come back.

I did have periods of weeks when the phone worked fine after disconnecting from te CK-300, but I dont know why.

I thought I had pinned it down to Firefox as it seemed to work fine after uninstalling Firefox but that was proved false after the last time I uninstalled it.

I have also tried uninstalling ALL applications using the App Manager but this hasnt solved it.

If you have some experiences in this matter that could be helpful.

Thank you.