Confirming on Linux 2002011108. This doesn't happen to me every time, but after trying a few times it does happen.
work in 6.2
Created attachment 65626 [details] Minimized testcase This happens everytime using WinXP on build 2002011103
Created attachment 67447 [details] Minimized Testcase This is a real minimized testcase
So click on "Minimized Testcase" and the symptoms emerge. When you click on a <CENTER>ed button, the button is left-justified and the onClick event does not occur. This happens iff a new window is opened without all the extra trappings. The funny thing is, if the button is more than half the size of the window, the onClick event *does* fire, even though the button is still left-justified. I am fairly certain this is happening in CENTER.
This got fixed somewhere. Reopen if you're still seeing it, please.