Since upgrading to Beta 12, I have noticed several occasions of the following:

When I middle-click on an application button (which should normally open a new window), instead I find that the existing window closes unexpectedly.

This appears to happen only on my secondary monitor, and only to Google Chrome (currently using version 18.0.1025.162). I confirmed that my config is set to have a middle-click open a new instance.

I apologize if this is a duplicate ticket. I tried reading the other forum posts, but none of them looked like they were the exact same issue.

Yes, running a fully-patched version of Win7, with NVIDIA graphics driver v296.10

It's possible that this is a fluke, and that the problem specific to me. I am reporting it now because I waited too long the last time I had an issue.

I will try rolling back and rebooting. Unfortunately the problem is intermittent (not every middle-click closed the window) so it could take a few days of testing before I give a verdict.

Upgraded to Beta 14 from last release to get the Beta 11 feature of merging pinned shortcuts. Works great except I'm having the same intermittent issue as Keith -- middle clicking on an application sometimes will close the application (with a 'safe' close with confirmation from some applications, as if I closed it from the window). I have not yet gotten it to open a new window. Reproducing the issue is difficult, but it seems to come and go in waves?

In fact it was not! I had no idea that this option was there. Perhaps it should default to the Windows default action of opening a new instance? Just to clear things up, the close window action (what middle click was actually set to) did become consistent after a reboot after installing the beta, where before the restart, it was very inconsistent.

Thanks for the help!