Safari error on opening .wmv and .pps file

I am using the latest version of Safari Version 4.0.5 (6531.22.7). When I am trying to open an attachment with .wmv file or .pps file, I am getting this error: Community Toolbar – We’re sorry, but the Safari browser version you are currently using does not support the community toolbar.
There are times that I can open the attachment without problems, but most of the time, I am getting the same error. How can I avoid the error message?
