3.74 x64. Firefox window sometimes becomes topmost

[cornflake]

Windows 7 x64. This might be a firefox issue because when I googled it I found a few reports of people who've experienced the same thing. I've had this happen to me once or twice in my x86 OS with my sandboxed firefox but today it happened in both the sandboxed firefox browsers I have open in my x64 OS and I'm not sure why. Basically the firefox window just becomes topmost for no reason. So when I try to click another icon in the taskbar it won't show because firefox is on top of everything else. Oddly there's no way to undo the topmost. I tried some developer programs I have that work to set or unset topmost on a window but they didn't work. I then wrote a test program and called SetWindowPos with the hwnd and set NOTOPMOST but that didn't do anything even though SetWindowPos returned one. Here's all spyxx showed for the firefox window when I sent the SetWindowPos

<00001> 00080A66 S WM_WINDOWPOSCHANGING lpwp:0039CD20
<00002> 00080A66 R WM_WINDOWPOSCHANGING

That's it. no CHANGED. 00080A66 is the window. It's so weird because there's just no way to take off the HWND_TOPMOST as a style. What I did was I restarted and everything is ok. I'm not sure what happened. Has anyone else had this problem? I didn't put firefox into full screen mode or anything.