I dont know which version of QTP you are using... I had the same problem when I tried working with ObjectRepositoryUtil inside QTP(9.5), Therefore I moved the code external to QTP...in a vbscript file...and removed a call inside QTP... Worked with ObjectRepositoryUtil independent of QTP
however it was working fine with QTP 9.1 inside QTP...
however it was working fine with QTP 9.1 inside QTP...