I’m seeing something very similar with 0.4.5-1+b1 on a laptop running amd64 testing. I can’t say exactly when this started, though, as yesterday was the first time I fired up the game in a while – pretty sure we were on 0.4.4-2 last time I ran it – but freeorion used to run fine on this machine.
Examples of issues are: very high CPU usage on a 2.5GHz i5; 15–20 sec. to process a turn right at the start of the game; multisecond lags when doing things like adding builds or techs to the queue; UI lockup/window-repaint failure; etc. I nuked my .freeorion directory, too, to no effect. I compiled from upstream source and didn’t see a dramatic difference from the performance of the Debian package. Best, -- Thanasis Kinias Doctoral Student, Department of History Northeastern University