5.5b1: Tab drawer gets visually corrupted
 

I keep running into a problem with 5.5b1 where the tab drawer gets all out of sync with reality. When this happens, I see one or more of the following symptoms:
[LIST][*]Long empty areas in the drawer where there should be tabs[*]I'll see a tab selected at the bottom of the drawer, but the content area of the window is showing the contents of another tab that isn't visible at all in the drawer (but should be shown below the tab that's shown as selected)[*]Unable to scroll the list, or it scrolls very slowly[*]Unable to predictably switch among tabs, if it's possible to switch at all (worked around this once with cmd-up/down, but not other times)[*]If I copy the list of tabs to another app, all expected tabs are listed, which suggests that OW's internal representation of the tabs is correct[/LIST]
The problem seems most likely to crop up when I'm opening several tabs from another app while leaving OW in the background (e.g., cmd-clicking links in Mail). However, I've not yet been able to work out any real patterns, and I may still be in coincidence area with the background links theory.

This didn't happen at all with the SP releases or any earlier release of OW that I can remember. Restarting OW seems to fix the problem, at least temporarily.

Anyone else seeing this?