this happens to me with firefox (but i would say a few seconds...!!!!)
this is because after some time and some manipulations, firefox is the default browser but not quite
(i guess chrome or internet explorer are stealing some settings...)
when i set the default browser to be firefox through the windows xp "set default programs" dialog, then all works again very fast
so in my experience, the use of the custom browser setting in FARR should work, but resetting the explorer could maybe fix something...