Hi, I have been able to reproduce that erratic behaviour and managed to fix it:
Download and install a new version of icon.library.
Get it from here http://eab.abime.net/showpost.php?p=814987&postcount=1
It is the "IconLib_46.4.360.lha" attachment in that post
Rename the 68000 version as "icon.library" and copy, replacing your old one into your Libs: folder.
Alternatively you can wait a couple of days when I release a new version of BetterWB and use the corresponding update to fix this.
BTW, thank you for the report.