Mouse Problem

I have an 8 button mouse. I like to use button 3 for 'double

clicking'.

For some reason unknown to me this button no longer performs this

function when I start W XP.

I then go to Start > Control Panel > Mouse > Buttons > Button 3 Double

Click > Modify > OK > Apply > OK.

After doing the previous I get a message " to protect your computer

Windows has closed this program, Name: Run a DLL as an App".

I close this message and get a second message asking if I want to send

an error report to MS. I close this message and my mouse button 3 is

now able to do double - clicking.

This will now work fine untin I close down W XP and then restart it.

Any help will be appreciated.