Yes, IE8 does still open even if I have FF open at the time. I tested that out last night because I saw it mentioned that it wouldn't. It does for me.
This is without question a CC problem, as I've now seen it on several different setups. On some only IE opens, even though FF is the default browser. Even on these setups if one were to change their default browser back to IE... then BOTH would open afterward. For me both have opened since day 1. I've even reformatted my PC since then, my setup is slightly diff. now, and the problem is the same. I think it's been established beyond any reasonable doubt at this point that the problem lies with CC.
CC is the only Piriform software I use, so I don't know if it applies to other products or not. And jwall... I have tried that file type edit you mention. That was my aforementioned "9 step process". It does not work. I've combed through all of those threads and tried every fix offered up, and none of them fixed the problem. The only thing I've found to fix it is to simply block IE from running through a Software Restriction Policy, HIPS or other. But then I'd have to re-write those rules every time I check for updates to CC, or Windows, which would amount to a bigger inconvenience than having 2 browsers open and therefore is moot.
So for now I'm just going to manually check this site for updates once a month. Like others have said, it's not a huge problem, but it is an inconvenience. What's more is it creates the impression to a first time user that the product is buggy and flawed, perhaps even malicious. When things pop open without an end users consent, that doesn't look good. Usually it's a sign of malware. You know how paranoid people are that post in security forums... something like this could easily start rumors that Piriform has gone rogue. I don't think I have to point out that that would not be in your best interest.
I don't want to make it sound like I'm bashing Piriform, or CC. It's quite to the contrary actually, I LOVE it! It's my favorite disk utility tool. This is the only problem I have with it.
I'd also like to add that telling people to modify system files and registry keys is not wise in my book. People will just end up breaking more stuff. The fix should be on the part of Piriform, not the end user.
Some info. about my setup: XP Pro SP3, Default Browser - Firefox 3.6.10, other - IE8, Avira Personal, Comodo Firewall+HIPS