I have the same problem. After a few minutes I just get disconnected from the skype server. Everybody still appears online on my side for a few minutes.(10-15) but I'm offline in others lists. This also happens during calls. I've
thought it would be from other services (Gtalk, Yahoo), but Skype is the only one which gets network error. I've disable everything and still doesn't work. Actually it drops the call whenever it wants, I had calls of 1 minute and call of 20 minutes. All over Wlan.
To solve it, I disconnect from the WLAN and reconnect, and most of the times it solves it, but after 5 minutes I have to do it again, other times it doesn't work and I have to reboot in order to reuse skype. This happens with or without other IM services running, but skype is the only one with problems.