Instant logout problem

Hi there,
I have no instant logout on my farming/ah character neither in the capitals nor in the inns for around 2-3 months. Sometimes it works randomly (once per 2 weeks). The character exists because its professions and its versatility to farm, I would not like to change it. I log in around 10-15 times a day to check ah and so on. Do you have any idea how to solve this issue? The character has already been unstuck in the account panel. I have no problems with my other characters.
Thanks for the replies.
Best Regards,
Fatpanda, Icecrown