but a rather long one .. 
AFAIC .. the information about LinkScanner Pro and FF3 seems to be confusing. (I do understand you're not using AVG) According to Exploit Prevention Lab's KnowledgeBase - Article 182, it reads:
Firefox 3 and LinkScanner
We are currently working on implementing support for Firefox3 into LinkScanner. The version of LinkScanner that is provided with AVGv8, will have Firefox 3 support in its' next release, scheduled for June 2008. The standalone version of LinkScanner will be updated shortly afterwards, however we do not have a definitive release date, at this time.'
The above was written on May 28, 2008. According to the Release History for LinkScanner Pro, the only version released after August, 2007 was your version 2.7.2 on July 28, 2008. It might lead one to believe, if the standalone version was to be updated shortly afterwards, it has yet to be. 
If you don't find the above confusing, maybe you can make some sense of this?
On Exploit Prevention Labs Support page for the standalone scanner, there's a paragraph titled "Known Issues". It's for FF3 and LinkScanner, which directs you to AVG's site. If you then go to AVG's LinkScanner FAQ #1458 (which "seems" to be current), it reads:
AVG Toolbar may not be compatible with Mozilla Firefox 3.0.1
The AVG Toolbar may report to be incompatible with the recently released Mozilla Firefox version 3.0.1. A fix for this issue is currently being prepared and will be part of the upcoming program update.
Again, I realize you're not using LinkScanner with AVG, but my guess is, it's not compatible with FF3. I may be wrong. But, if I were you, I'd contact them and ask if it IS supposed to work with FF3. And if so, "how". Otherwise, I'd ask for my money back! Choice is yours. Try either of these, if not both:
http://www.explabs.com/contact/
http://www.explabs.com/support/form.asp
Needless to say, I wish you the best of luck..
Carol