I believe it's the new RR and the new RR config.
I have done a system restore to a previous version of RR, and when i hit the volume buttons, the respond immediately... in face i can see each number whiz by from 0-10.
In the newest version it delays, and when i hold the button down, it can jump from 0-100 a few seconds later, as it seems there's no response.
I'm not accusing anyone here, but that's what worked for me. I can't really imagine why though.
BTW my specs are listed in profile, with a 11 second cold boot so i assume the PC is not that slow.