Hello mhf,
I use K-meleon too, my default browser.
just follow the scott's advise (1st. link by rednose), it will do the trick.
of-course unlike avast4, avast5 use the new ini file, webshield.ini, located under all users profile folder,
for example on my win xp it is at "C:\Documents and Settings\All Users\Application Data\Alwil Software\Avast5"
2nd. link of rednose, also works, and you don't have to change the .ini, but it's slow down KM (at least for me).
HTH