My sitemapper 5.3 also locks up when running on www.primedesignusa.com.... sometimes! and then only on the same page. it has a .gif on it, none of the other pages has an active gif. Perhaps this is a problem. Also, I am running W7 64 bit. the page with the gif is the .../mechanical.htm page
That would have no impact on the software. Probably has to do simply with the fact you are on a 64-bit system. Have you tried this:
1. Right-click the program .exe file and select Properties .
2. Click the Compatibility tab.
3. Select the Run this program in compatibility mode for checkbox and select Windows XP .
4. Click OK