User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:2.0b5) Gecko/20100101 Firefox/4.0b5 Build Identifier: Mozilla/5.0 (Windows NT 5.1; rv:2.0b5) Gecko/20100101 Firefox/4.0b5 Just after updating to firefox 4.0 beta 5 from beta 4. The area around the scroll icon (that appears when you press to scroll wheel on your mouse) shows the content that the icon was previously over. The patch of reflected content disappears when you click on the page then scroll up or down using the scroll bar. I will add a Screenshot Attachment. Reproducible: Always Steps to Reproduce: 1. Go to any website. 2. Press the scroll wheel and scroll. Actual Results: The area around the scroll icon displays where the scroll wheel is first pressed. Also, it stays there when you press the scroll wheel again. Expected Results: The scroll wheel should pass over the page displaying what is under it at the time. I was using the default theme. Using: Adblock Plus 1.22, NoScript 2.0.2.5, Microsoft .NET Framework Assistant 0.0.0, Java Quick Starter 1.0, Browsing Protection 1.10 by F-Secure, Feedback 1.0.3 Build Config: about:buildconfig Source Built from http://hg.mozilla.org/mozilla-central/rev/58575263536b Build platform target i686-pc-mingw32 Build tools Compiler Version Compiler flags d;D:\mozilla-build\msys\mozilla-build\python25\python2.5.exe -O e;D:\mozilla-build\msys\builds\moz2_slave\win32_build\build\build\cl.py cl 14.00.50727.762 -TC -nologo -W3 -Gy -Fdgenerated.pdb -DNDEBUG -DTRIMMED -Zi -Zi -UDEBUG -DNDEBUG -GL -wd4624 -wd4952 -O1 d;D:\mozilla-build\msys\mozilla-build\python25\python2.5.exe -O e;D:\mozilla-build\msys\builds\moz2_slave\win32_build\build\build\cl.py cl 14.00.50727.762 -GR- -TP -nologo -Zc:wchar_t- -W3 -Gy -Fdgenerated.pdb -wd4800 -DNDEBUG -DTRIMMED -Zi -Zi -UDEBUG -DNDEBUG -GL -wd4624 -wd4952 -O1 Configure arguments --enable-application=browser --enable-update-channel=beta --enable-update-packaging --enable-jemalloc --enable-tests --enable-official-branding