Synfig speed issues

I have lately speed issues with synfig. Even considering the fact I have pretty new computer (Geforce 9600GT, Intel Core2Quad Q9450, 4GB ram), Synfig pretty often hangs with text “Rendering…” in status bar (during normal edition of animation, not actual rendering) after zooming in/out. Sometimes I have to kill synfig (fortunately Ctrl+S combination works so no data loss). Even tried to check in system monitor what is monitor/processor usage and processor is used in about 65% (including synfig) and memory is used 1.5GB out of 4. If that helps currently in my system are running:

-Chromium web browser (40 tabs)

  • KNotes
  • KDE 4 with enabled composition
  • VLC Media player
  • (Polish instant messenger)
  • KDE System monitor
  • Amarok
  • Skype
  • Dropbox
  • Manic Digger server (MD is well-made Minecraft clone and it’s entirely free)
  • HP drivers manager for my printer
  • Orage

And of course synfig.

Can we know which files are you editing when it hangs rendering?
Are you using the latest stable version or a release candidate?

I use 62.02. And the file is simple file with character (less than 200 vertexes and number of curves is about 50) for my animation.