It's not an error so much as a notification that your client has disconnected for whatever reason.
Is it occurring exactly every hour and a half or is that just a rough estimate on your part?
How do you connect? Is it wireless?
Can you go through the suggestions here?
A couple of the first few steps are obsolete I believe. Joining the General chat and enabling Secondary Logon should not be needed any more, but the rest could still apply.
Honestly, I'd get off wireless first and see if that's the cause. If it is, you can take steps to improve the signal and limit interference. Joining or leaving channels is easy though. I don't believe being in them really does much any more. It was sort of an urban legend fix going around early on but it doesn't seem to have much of an effect that I know of. I don't join any channels when I play at home or here and I never disconnect. I also don't know of any problems with being in 4 either.
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