i found when i select multi files Especially select file>50 files, the selection area rectangle very slow, and high cpu usage. 1.6.10 and 1.6.11 both have this issue.
Thanks for reporting! .. just saw there is an duplicate bug. Actually you reported first, however the other bug already has alot of comments, so I will close this one. *** This bug has been marked as a duplicate of bug 14026 ***