I'm having a similar issue at
Debian Jessie 32 bit, Lazarus 1.6 (at work)
Still everything works perfecly in
Debian Jessie 64 bit, Lazarus 1.6 (at home)
I can copy-paste between Lazarus code, but not outside the Lazarus Window (even no copy-paste between Lazarus instances). I haven't analyzed the problem thoroughly yet. Maybe I've caught some sort of clipman bug at my work PC? Because the OS installations are almost identical.