open doesn't work in right click

From three days ago when i want to open more than 1 files
with "open" in right click,nothing will happen,but if i press enter 
button all of selected files are open!

I  tried it with PDF,word & excel files, and the result was
similar.It is necessary to say that for 1 file "open" is working but for
more than 1 file not.

The last software that i installed is: spy-bot and for 1 week after
that all things was nice but from 3 days ago i have this problem:-(

I am using Windows Server 2003r2, eset antivirus node 32 endpoint and have 6 GB of RAM.

How can I resolve this problem?

thanks in advance.