stickmaker | RealPlayer Problem

Finally gave in and downloaded and installed the free version of RealPlayer on my iMac. Most of the files I've tried have played fine, but two (so far) which I know work on my Windows machines are really choppy, playing a bit and stopping a bit over and over until the thing is finished. And RealPlayer won't respond to anything except clicking on the Dock icon to open the menu. _Then_ it plays fine, until I close the menu!

Anybody got suggestions?