Try deactivating all plugins and check to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).
Switch to the default theme to rule out any theme-related problems.
Rename the plugins folder via FTP
Also see:
http://ww.wp.xz.cn/support/topic/279132
Thanks for the answer, i tried both solutions, but it makes no differce.
Disable Google Gears if you have that running/installed in your browser and empty your browser cache.
Finally see if anything in http://ww.wp.xz.cn/support/topic/279132 helps.
No Google Gears here. I installed a previous version of the plugin and that works fine and reported this to the maker of the plugin.