Thanks for the response. If I apply an effect and backup the position indicator, say 5 seconds, the playback stutters within a second or two and plays the effect fine! This happens only after I add an effect. No colored lines appear at the bottom of the timeline. The 4 drives are: Avid Ultra 320/LVD (computer: hp xw8200 with 3G RAM). It seems to be some sort of a buffer problem; but the same problem on 3 systems?
Could it be a networking issue? This is the one factor all systems share besides all using Media Composer software?