Esenthel 1.0
I was encountering this issue for a very long time now, but I just recently discovered the source at last. If you scroll up and slow the camera movement as much as possible, you're no longer able to hold LMB, move the mouse creating the rectangle and release it to select many objects. The rectangle just don't show up any more until you scroll down to some point.

I hope it will help.

Many thanks for finding that problem it will be fixed for next release.

No problem, thanks.