Opera 12.00 alpha missing minimize,maximize/restore and close buttons bug & workaround

This happened to me with both the 1105 & 1116 builds, and the workaround was the same in either build, so I'm posting it here for anyone else running the windows builds. I am running 64 bit vista, and Nvidia video drivers. I was going a little nuts over the fact that my buttons kept going invisible after a while, and found out two workarounds.
The first is to turn off WebGL hardware acceleration. Don't know what else that does, but it changes the look of the default skin and brings back my minimize, restore and close buttons.
Interestingly enough, the second workaround is to apply a skin/theme. That works too, and it does not seem to matter whether or not I have WebGL on or off, my buttons stop disappearing, and my interface looks nice too. WebGL renders fine with on my machine wit hardware acceleration enabled on 1116
Somehow, the default skin is just not rendering the buttons properly when hardware accelerated WebGL is active on my device. The new skins do not have this problem, as I tried several of them and had no issues.

Note that there is a bug with applying a theme - clicking on the task bar icon to minimize a window will no longer work. (Clicking to restore a minimized window works fine.) Clicking on the theme's own buttons does work, just not the task bar.

I had this problem yesterday in version 11.xx. on my Windows XP SP3 desktop computer. I read solutions online which recommended deleting: C:\Documents and Settings\YOUR-USER-ACCOUNT-NAME\Application Data\Opera\Opera\operaprefs.ini

SOLUTION:
The real root cause of the failure is the file which contains saved "sessions" or basically all open tabs of web pages:
C:\Documents and Settings\YOUR-USER-ACCOUNT-NAME\Application Data\Opera\Opera\sessions\opera.win
Opera.win is actually a plain text file that can be opened with Notepad.

After upgrading Opera to a new version, which did not solve the problem... I started opera and clicked on each tab and copy /pasted the open url into a notepad text file. Then I pressed Alt + T for the Tools menu, clicked on Preferences, in the General tab look for "Startup" in that drop down list, be sure to choose anything - but DO NOT CHOOSE "Continue Saved Sessions" as this will automatically open opera.win file which contains the error that caused the problem. Finally, you need to click File, Sessions, Save this session so Opera will overwrite the default opera.win or you can
delete: C:\Documents and Settings\YOUR-USER-ACCOUNT-NAME\Application Data\Opera\Opera\sessions\opera.win.

TIP: it is often better to close opera and rename a file such as opera.win to opera.win.old rather than delete it. This way you confirm that that file is causing the problem. If it is not then you can easily restore it. For the detailed power user then could actually edit it and by trial and error discover the exact line that is causing the problem. Note: it is possible for a file to contain a non-visible character which could cause a problem.

Enjoy.

And you posted to a year old thread to say this?