File Vault trouble?

I'm a bit paranoid about security, that's why I use File Vault on my laptop to protect sensitive (client) information. However, that might have nasty side effects, as I think I've uncovered. Let me quote my posting on Apple's discussion forums:

When travelling abroad, I've repeatedly encountered very serious system instabilities, involving the loss of application preferences, keychains and other vital system information. This was always easily recovered by restoring the backup back home. But naturally, the home backup is not really handy on the move ...
I think I've narrowed the cause of these instabilities now down to a combination of using File Vault and changing the time zone from the account that is protected by File Vault. Is anyone unfortunate enough to be able to confirm this, and might any expert out there have an idea about a plausible explanation and fix for this? Thank you very much!
Incidentally, the workaround (short of not changing the time zone) is changing the time zone in a user account that is not protected by File Vault.

I hope someone can comment on that. Meanwhile, don't try to replicate this on the move, and be sure to have a working backup!