Problems with HTML Variable name – special charater failure

Hi support team,

I have the problem, while setup within e.g. event settings of the a post custom field within custom fields area, the HTML Variable name will not be saved. The name would be “service_onl._booking_link_own_(prepaid)” or either while trying to use just the underline figure “service_onl_booking_link_own_prepaid” both versions are not savable or usable.

Failure: Please do not use special character and spaces in HTML Variable Name. (screenshot – http://screencast.com/t/Z5LT7EntHGam )

Please advice why or which special fields are not usable and how to enable that. In former geotheme it was working. I need to have at least the “_” figure to enable much filters with different names to identify for.

Thanks, Alex