I still seem to be having this problem. Left clicking on a link to a PDF file causes the computer to lock/freeze, and it has been like this ever since getting a new motherboard last year. Right clicking on the link and downloading it to the desktop means it can be read. I'm curious as to why this is? Doesn't the machine need to download the same file in both cases?
On a different note, this PC does not have Powerpoint. Can a ppt file be opened using Word or IE or other programs?