When clicking on the minimize button (in the window border), the button itself sometimes starts to flicker like crazy and Firefox does not react to any user input anymore. It is possible to bring FF back to normal when minimizing the window via clicking on the browser task in the Windows taskbar, but that does not work when several windows are open and Task grouping is active (which causes clicking on the Firefox task in the taskbar won't minimize but bring up the opened windows). I'm still trying to find out what actually drives this behaviour, but I noticed this bug on all (Windows-)systems I have tried.
Duplicate of Bug 535619 ?
It's a bit different in this case: The window control is redrawn at a bizarrely high fresh rate and the UI event loop is totally overloaded. Things often slow down when waiting 5-10 minutes after the "minimize click of death", but not always. The UI load also causes Firefox to eat a lot of CPU in this case. I'm also using x64 builds of Win7 btw.
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