Unable to open urls – inconsistent

I have a user using Outlook on Win2kPro. We have an internal POP3 mail server. User’s mail format is set to HTML.
The issue is, the user gets newsletters from a vendor with links to their website in the message. Instead of acting as a mail message, it acts like the user is replying to the message and places the cursor in the message area as though the user is editing the message.

Weird thing is, after a reboot the links work fine, yet a couple of days later, the same issue arises. This is not isolated to one particular sender, either. I tested sending the user a url from my internal email and it had the same effect.

Anyone ever see anything like this? I’m stumped.
Thanks,
Val