DD-WRT applyuser.cgi hangs

What to do if you're running into the issue with the DD-WRT admin page hanging on the applyuser.cgi script when you try to save changes.

SYMPTOM:
when you click 'apply' you get directed to the address -

http://192.168.1.1/applyuser.cgi

Which is followed by a blank white screen. Navigating back just proves your changes were not affected.

SOLUTION:
restart the browser - it's probably just a cookie with a hung up user session or something, but I couldn't find it. Other suggestions would be very welcome...