Well, that's wrong. Anything you can suggest about your environment that might be causing that? Oddball graphics card, old drivers, laptop, running on linux, etc.?
To answer your question, though, I'm not near Newsbin atm, I'd be digging through the prefs just like you though. Someone else might know offhand one way or the other.
[EDIT] ah, yes, of course, you're posting in the linux forum...I just go through the new messages and miss that sometimes. Yeah, it's obviously a wine issue. As far as being able to disable, no, sorry, I haven't been able to find an option to disable them in the latest. I'm going to fire up the latest on my linux machine and see if I can repro...
[EDIT B] OK, I've tried the latest(not released yet) and I don't see this behaviour, the grid lines are quite well behaved. Tried resizing NB, min, max, scroll like mad, etc. Of course, there's several variables. I'm running on the latest suse, which really in my experience the distro is very, very rarely related to issues like this, it's almost always the graphics card, driver and the release of wine you're running. I'm running a decent older nvidia card(9800gtx I believe) and a pretty recent driver release - 290.10, and wine 1.3.30. It's hard to say if it's related to exactly how many posts it takes to trigger it - are you saying you don't see this at all, but suddenly large loads trigger it?