Losing Left Mouse Click

As a test, try creating a new admin user account in System Preferences Accounts pane

http://docs.info.apple.com/article.html?path=Mac/10.5/en/8235.html

Log out and log in to the new account. This will help to isolate the cause.

If this problem never recurs in the new account, the problem is likely to be something in your normal user account. It might be some corrupted or mis-set user preference setting. It might be a background process that runs in your normal account; check System Preferences Accounts pane +Login Items+ tab for any login items (processes that start automatically at login) that may be related to the mouse, and remove anything that should not be there or you no longer need.

If the problem does recur in the new account, the problem is likely to be at the system level, or related to hardware. Is this a third-party mouse, or an Apple mouse? If third-party, does it use a special driver. If so, it may be related to the driver; make sure you are using the latest available version from the manufacturer's web site.

This issue just started to happen to one of my machines as well.

No luck on second user, I tried that first. Weird thing is, when I remote login to the machine from ARD, I can click... so it's definitely a system software thing.

I am considering an Erase and Install or upgrade to Snow Leopard next.

It might be a faulty mouse. It would work fine for remote access, because you are not using that mouse. If it's a Mighty Mouse, it has sensors on the top surface so make sure it is clean. Also, make sure you are not touching the scroll ball when you do a left click; touching the scroll ball will register as a center click and not a left click.

If you have another USB mouse, even if it is not an Apple mouse, try connecting it. If the left click works consistently with this other mouse, it is probably not related to the current system installation.

i have a very similar problem on both my macs since installing snow leopard. when browsing with multiple tabs the mouse looses its left click and substitutes a right click for it (which is hugely annoying), this occurs on both the macbook pro and imac. so it is not a hardware issue.
the only way to get it to work again it to call up the system preferences window and click in that. we are then back up and running.

any ideas anyone?

Same problem. Replaced mouse. I disconnect/reconnect mouse from keyboard then it works.

Help - I'm having the same problem, on a PPC G4 Mac Mini running OS X 10.4.11. Happens with every mouse, whether it is plugged into USB or running via Bluetooth. Restart usually fixes it for a while then the mouseclick goes away again. The weird thing is if I do a "screen sharing" from another computer I can click just fine. Very frustrating; can anyone help?