When running nethogs on a system that misses some uid->username (f.i. a VPS root node showing traffic from processes owned by some user in a client node), nethogs exists with 'assertion failed'.
Fixed this with a nice patch, against 0.6.1-pre2
Tom Hendrikx (alt. account)
Do you know whether getpwuid() sets errno in that case? The latest version of nethogs will show the UID, but only when getpwuid has left errno untouched.