I experienced this problem or something similar earlier this year.
Explorer would crash if a) the taskbar was right clicked in the centre region (but not if clicked in margins defined by skin) or 
Drop down menus (file, edit, view etc) were clicked in explorer windows.
MSN Messenger would exit cleanly if a) It's status icon in the tray (notification area) was clicked (left or right) or Drop down menus in messenger were clicked.
Windows Media player would crash if a) the video area was left clicked, or drop down menus were clicked.
notice a trend?
All the above problems would be resolved by unloading WB.
All the above problems were also resolved by creating a new skin, not changing anything, and using that. (i.e. using WB to make xp look like xp.)
Messenger and Media player both survived drop down menus when they were excluded from skinning.
All the problems but the media player video left click were resolved in a given skin by altering the use of transparancy, paint methods, margins and intelligent shrinking for the taskbar and per pixel window margins (much trial and error). the use of UIS style window borders also fixed the menu drop problems.
From the above - problem deduced to be due to the way in which per-pixel transparancy was being handled.
I fixed it temporily by using skins which did not include any of the problematic features -(using UIS frames/modified perpixel/non transparent taskbar)- but WMP still crashed if video play was left clicked. Applet written to test overlaying two or more perpixel transparent objects also crashed if three or more were overlaid. New graphics card drivers downloaded. problem persisted. report sent to nVidea. (if it happens when not using WB, just other perpixel transparencies in windows xp, is probably graphics card or drivers fault) WB was just first symptom, owing to much transparency use.
Since then I've altered more of the system, downloaded SP3 and another set of graphics card drivers. recently rechecked the problem, and is resolved. Unsure if this is due to the new drivers, SP3, or the other bits of the user interface, OS, and assorted third party or self written things that have been added, altered or removed in mean time.
I am running a highly hacked, chainsawed and spraypainted version of windows xp Professional (32bit) SP3 on a core2quad Q6600, 4Gb RAm and an Asus 8800GTX 768 graphics card. WB is version 6.4 build 73 x86
When problem existed was running same machine with a slightly more chainsawed version of windows Xp SP2 (with significant chunks of SP3) and same version of WB.
Problem had not occured with demo version of WB, possibly earlier version late last year, when was running H'dCS'd&SP'd windows XP Professional sp1 with most SP2 elements and a couple of SP3 bits.
Advice to others i derive from this:
Step 1) unload WB. problem persists - probably not WB's fault, but I have no further help for you.
Step 2) Update to SP3 if not already using it.
Step 3) Update graphics drivers, especially for nvidea 8 series
Step 4) Check if problem persists, and if it does, tell your graphics card manufacturer, stardock and microsoft.
Step 5) Limit use of per-pixel transparency, and await a solution
Step 6) DO NOT attempt to rewrite your graphics card drivers.
