Security / Firewalls :: Cannot Open Or Save Email Attachments

I have an old Win XP (SP3) desktop that just recently has a problems with attachments to emails. It simply won't allow me to open or save them.

I have tried both hotmail and btinternet.com (yahoo) emails. When I click on an attachment and choose either 'open' or 'save' the small grey box appears that usually shows the file action and download time info. However no info appears in the grey box and it just sits there (for hours). I have tried the same email attachment on another PC and it works fine so the problem is specific to this PC.

The file size is not a factor, as it fails to open attachments of only 100kb, nor is the file type (pdf). I can download large pdf files from a website with no trouble. the problem is just email attachments.

I tried switching off the Windows firewall, but this made no difference. The a/v is AVG9.0.