RealPlayer Problem

[stickmaker]

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?