If dilettante's link did not help (if you even looked at it) then make sure you run VB6.EXE as Admin all the time.
If that did not work, unregister (might not be needed) mscomctl.ocx and register it again using CMD Prompt (run as Admin!), and use regsvr32 to register.
Maybe your mscomctl.ocx is corrupted, try getting a new copy (not sure where but somewhere). Which service pack do you have? I have SP1 with windows 7 home premium and I have IE10 installed with Microsoft Office starter (2010), and lots of other programs installed (Ex: VS2010, VS2012) and NEVER had a problem with any ocx files!
I know this is an old thread but I lost a day to this problem and it turned out to be something simple in my case, a bug I think in the IDE. There seems to be quite a few reasons for this happening but I'm trying to spread this solution around as much as possible. It may work for someone else too so its worth a try:
Tick the following:
Microsoft flexigrid control 6.0 (sp6)
Microsoft MAPI controls 6.0
Microsoft Masked Edit Control 6.0 (sp3)
Microsoft Tabbed Dialog Control 6.0 (sp6)
When you try and add Windows Common Controls 6.0 (SP6) it no longer gives the message '' could not be loaded." instead it changes to "already in project" If you quit out and load your project you will find it will work again properly. Hope this helps.