I faced same problem many times, I usually ask developer to access my machine through Team Viewer so that developer can view exact steps I followed to produce the bug and then he can do the necessary to resolved it.
first and fore most thing i feel is to check the build version of the developer and QA analyst.
tester can send his steps to developer along with screen shots and request the same from developer(detailed info).
check for the browser type qa and developer using.
check for the versions because ff3.5 and 3.6 do not behave same for my project.