I have the same issue, so I can confirm the thread starters problem. I'm sure the issue is the same as mine.
I set "Default View: to Flat in the fireboard configurations, which seems to work fine in FF & Safari browsers, However in IE7 Guests see a threaded view even though I set Flat as default.
I'm guessing this is isolated to IE. Once flat was selected manually as a guest, the threads were fine again in IE. I'm just curious as to why the FLAT view is not staying default in IE7?
Any assistance would be appreciated in this manor.