Hi Joachim,
It was not only you:)...this got fixed in 8.5.1.
To reproduce:
1) Open any Appliction/Class/Method browser
2) Set a breakpoint anywhere on a method
3) Click the "red ball" breakpoint widget and immediatley (< 5 seconds) close the browser
4) Wait for 5 seconds
Quick patch:
Change "self updateInformation" to "self shell isDestroyed ifFalse: [self updateInformation]"
in EtBrowser>>singleSelectBreakpointTag:clientData:callData:
-- Seth