Left click doesn't open messages

In Thunderbird and ACDSee and some others like Photoshop, my left click no longer opens files. I have to press enter or make a right click menu selection. It always did this before.
It moves focus, but doesn't go to enter or complete either a single or double click.

I've gone to every dialog box in Win 7, and ACDSee and haven't found what is wrong. I even re-installed my mouse (MS Intellipoint) drivers. It doesn't work with my tablet mouse either, so I can only assume the problem is with Win 7.

Any ideas? ?????

I forgot to mention that the left click works fine in Windows Explore and opens desktop icons.

ACDSee is my preferred file and photo manager though. And I handle all my mail in Thunderbird. But they feel crippled without the normal left click functionality. ?????????????

Try this:

Close any open programs> Start> In search box type run and press enter> Type

regsvr32 urlmon.dll

And then click OK (note the space between regsvr32 and urlmon

You will get a message like the DllRegisterServer in urlmon.dll succeeded> Click OK

If this does not work, repeat the steps for each of the following files (in step 3, replace Urlmon.dll with the correct file name below)

Shdocvw.dll
Msjava.dll
Actxprxy.dll
Oleaut32.dll
Mshtml.dll
Browseui.dll
Shell32.dll

Let us know if it helps. A Guy