In addition to the problems I have had with rendering time lines with reversed clips, I now have another anomaly going on. It seems that if I try to do something to a clip that requires any form of rendering, the timeline and output window will not play back after CS3 has rendered. The only way to resurrect the feature is to shut down Premiere, navigate to C:\documents and settings\username\adobe\premiere pro\3.0\ and delete the preferences file. Then restart premiere, open the project by finding it on the hard drive (because deleting the prefs file removes the list of recent projects) and hey presto the timeline will now play with the rendered file.
OK, if anyone is interested, I think I've worked this one out. I have two nVidia quadro fx 3500 graphics cards and Premiere seems to get confused with the dual monitor setup I have. For some strange reason I had my #2 card & monitor as the primary display and the #1 card and monitor as the secondary display. I had Premiere's output monitor and the timeline on the #1 (secondary) display which seemed to confuse the hell out of me let alone Premiere. Having re-arranged Premiere's workspace so that all the working windows were on the same monitor Premiere worked fine. I will now re-arrange the cards and monitors so they are set up as #1 the primary and #2 the secondary and see if that works with the working windows split between the two displays.