It is not a good idea to use the Real Player as a stream recorder.

There are many ways to record http:// .flv videos from freeware browser plug-ins to freeware download managers like Orbit Downloader:
How to record/download/capture/save Macromedia/Adobe Flash .FLV video HTTP stream from embedded player

I had no any problem recording with Replay Media Catcher and NetTransport.

p.s. After starting recording it is a good idea to stop/pause the video in the embedded player (unless you use WM Recorder in the PRO mode or FLV Recorder).