Virt-manager lags

Hey guys!
I tried to instakll virt-manager and to use t for some distro tryouts (example: easy peasy and zenwalk rigth now), but I noted that, graphically, it is subjected to some lagging issues? Is this a problem of mine? I notify that I use statler and that I don't have proprietary drivers installed (Ati radeon), cause I don't need them... Could this be the issue?
I tried changing the display driver of virt-manager from cirrus to vga, but result is the same... Any sugestion?

Thanks in advance!