OK, I've read through the logs of your first three boots (up until 22:46). I'm really not sure what the problem might be.

You're still getting errors about communication with the SIM, but I don't think these are the root cause but merely a symptom. Likewise I don't think cleaning your SIM will help; the problem seems to be elsewhere.

I recant my earlier statement about your carrier not being able to help. Perhaps you should consult them to see what they can add. I too could believe your N900's IMEI has been banned on their network. It's worth asking them again; perhaps their customer services database isn't yet in synch with the production database.

It would be nice to know exactly what rc:4 indicates in this message: "cellular: csd[758]: ISI_SMS .790557> ind_reg_status(): Net registration (ind) status:0 rc:4". I'm having trouble finding that message in the various sources I've consulted on maemo.gitorious.org. I can't find anything on bugs.maemo.org that seems relevant.

I'm not sure, but conventionally negative return codes are rarely a good sign. It's late and I must sleep. If I have time tomorrow I'll install syslog to see what results I get.

As the SIM works in your N95 you might try deleting all stored contacts and SMSs. This is just grasping at straws though, based on where the majority of your errors are reported.

One other thing to try would be forcing a 2G connection, rather than dual or 3G mode.