Change my username on forum?

Initially I registred on OSM with login "Roman Shuvalov". Then I changed it to "romanshuvalov", but forum account kept "Roman Shuvalov" and I thought it's okay. After over a year of using OSM I logged out from my account on forum for the first time and suprisely found out that I can't login to forum. Forum account "Roman Shuvalov" is not accessable anymore. I only can to login via "romanshuvalov" name so I lost my access to my real forum account.

Is it possible to delete current "romanshuvalov" forum account and rename old "Roman Shuvalov" to "romanshuvalov"? (Problem is only on forum; this helpdesk, by the way, worked fine.) I believe that forum moderator or administrator can do it.