It could be a conflict with Bridge, which runs continually in the background -- even when you're installing other programs.
But it's hard to say, without knowing anything about your system, its hardware or operating system.
I had no trouble with E10, so i thought it might be more of a 64 bits issue.
ssd for W7, i7-940, 12 gig ram, raid0 for editing. extra disk for export, media cash.etc.
I had a hard time installing E11 due to No shared components or something.
Ran the Adobe Diagnostic app: the error it gave me: A restart is Pending.
Followed the fix http://helpx.adobe.com/creative-suite/kb/troubleshoot-error-messages-bootstrapper-cs5.html But there was no InProgress Key to delete. Maybee it's a ssd and not a regular drive. Just guessing.
Deinstalled the whole CS6 suite and E11, use cleaner tool.
Then after a few installs en de install E11 finaly installed without an issue.
Later on I found Encore crashing.
Deinstalled the suite, ran cleaner tool (several times) but now show.
Deinstalled all of adobe.
Installed CS6 again, can't do without Encore.
E11 is just for instruction purposes, cant use it as it does not support Canon's mpeg2 codec.