Oh.. that's odd, i don't usually have a problem... hmmm.. i only forget norwegian if i have been using too much swedish... i use both frequently, although usually only writing and reading, as I don't call my friends as oten as I could due to phone bills and slight time difference etc etc etc...
I wish I could have spoken another language as a kid (not including compulsory French) as it was I had to teach myself Swedish... as for Norwegian it was extremely easy to pick it up after some weeks of living in Norway... I have never studied either though, that would take the fun out of it, I think
Hmmm.... I'm intrigued as to what sort of trouble you could get yourself into by using a language....?