I have been having the same problem, and I think it may be related to Roxio or similar drivers, as it seems to be the only consistency that I can surmise, and this is the 3rd time I've experienced this problemd.
I proceeded to post this very question in the Alcohol support forum, but that became suprisingly similar to being as much fun as doing taxes, as the UI was not as straight forward as I had hoped, and I had to play email tag with support. I did eventually get everything resolved, but forgot about this issue until I just now ran into it again, and decided to do a search to see if anyone else had run into this and found a solution.
I used to be in support, but it's been years, and I am not up on the learning curve with MCSE-related admin (I crossed over into a new field after the NT4 MCSE when I heard MS was going to discontinue the tract, prior to all of this becoming a stink with everyone, and MS eventually relenting), so if I need to post anything for anyone else to help those of us seeking a solution in this thread, please let me know if you're up to helping, and I'll post what is needed. I have HiJackThis, but only a general understanding of it in that it gives you a comprehensive view of drivers loaded, etc. Would that help in this case if that were posted by those of us who are having issues?
Ok, probably too much info, but I'm on a roll, the coffee is still hot, and I just took my vitamins, so bear with me.
I was loading and unloading my .iso images via the R-click in Windows Explorer, which works great for me (using Alcohol 120% v1.9), and then I upgraded to the latest version, 1.9.5 (Build 3823), which is apparently now outdated from the new version available message I am getting upon opening the program. Now, I just went to change my .iso images on my virtual drive, and it took over 10 minutes for the CD to become available (the virtual cd setup by alcohol).
I also remember installing my Roxio EMC 8, and I'm pretty sure that's when the problem started. It may also be Nero 7 Premium as well, as they both have more "tools" they try to load by default, which I have not taken care of at the moment, but usually do.
I would suggest that those of you who are not familiar with hardware support or A+ Techie type of stuff, check and see if you are running any programs for any CD-Burning software. If you don't know how to do that, post it in here and maybe someone can post a short version of how to do that. I would do it now, but I'm kind of in a time squeeze right now, and wanted to get this posted.
Anyway, I just wanted to post here and let those of you who are having the same problem to try and get all of your "resident" CD-Burning software ended via the Task Manager, and see if that works. You may need to dig deep on that, but tread lightly, as you don't want to mess your system up, and if you're not comfortable, keep reading on and post what you're not sure about, and people in these forums are usually very helpful as long as you're trying to solve the problem, and not expecting people to do all the work for you.
Hope this helps, and I'll dig up more info and post it if your solution hasn't been found yet.
Sorry for the long post.