KPSK <-> gMFSK - Soundcardproblem?

Hallo OMs! After a lot of "wasted" time trying to make a PSK31-QSO on the HF-bands I checked PSK31 with a friend in the near on UHF! First I wrote his transmission with KPSK - very fine! Then I tried to transmit - He said "terrible signal!". My Signal was very loud but there was only noise on the frequency! After 1 hour I tried to transmit with gMFSK: All clear! Very fine Signal! ???? I believe, that this behaviour can't be affected by the soundcard!?!?!? Can anybody help me, I want to use KPSK for PSK31, because it is more convinient I think! Looking for help! Yours Peter, DL3VPZ. PS: I've checked the KPSK-list for soundcard-problems but I think, nothing belongs to my problem?!?