Ok ,this might sound stupid but I am sure I am not.
I don`t know exactly why but it`s true. I am using portableapps on my harddisk (d:\...) aswell too. If I format c:\ and reinstall windows then my accounts and passwords are not longer saved in portable gaim.
The otr files are deleted aswell. But gaim is still startable...
I am almost sure you won`t belive me. I guess gaim will delete the settings on gaim`s first start on new system. Perhaps it`s not portable gaim`s failure, but otr`s.
I have not really an idea... The only thing I can do is using File Mon and take a screenshot next time I am doing this. Isn`t a very common bug.