Six months ago, I decided to use the new HomeSite version (4.5) and saw this problem. I never found how to solve it. My only solution was to uninstall HS4.5 and reinstall HS4.01, wich works great.
I noticed another problem with HS4.5, when you uninstall it, you MUST unregister some DLL's manually (this is a allaire's known problem). Explanations on the allaire's website.
As a conclusion, I don't know what to do, just to install a previous (and more stable) version of a great but very bugy software 😉
Regards
olivier