Conversion error when trying to update story points from Agile Planning Board

I was trying to follow "White Belt" Greenhopper article, but cached an error while trying.
On the Planning Board every issue box has "Edit Story Points" control. Every time I try to change that value I got error, for example: "2.0 is not a valid number".

Please see attached:

• error details from "catalina.out" (last error message in file)
• error window in .jpg file

Changing Story Points from edit issue screen works fine.
I guess it may have something to do with regional system settings for Poland. We do not use "." (dot) as decimal separator, we use "," (comma) instead.