maya - dodgy timeline

hi!
please could anybody help me with my timeline in maya?
ive got 8.5 and 2008 and they both do the same.
when i do simple turnaround animation it just wont playback smooth but kind of snappy pretty much similar to linear keying...
might be my pc as the both versions are doing the same but i dont know how to fix it...please help!

thanks! marcela

don't play on view port ,it won't play real time.
try doing play blast.(right click on time line)

Make sure that you have selected playing Animation as "Real time 24fps"