Filevault login screen slow to start after trying to install Windows using bootcamp Since trying to install Windows 7 on my iMac with Lion 10.7.4, using Boot Camp, I noticed that the login screen where it asks for the FileVault password is taking a lot of seconds to be displayed. 

When I turn on the computer, after the sound only a blank screen is shown for a lot for seconds.

Even after removing the Windows partition using Boot Camp, this slow down persists.

Anyone with similar problem, or solution?
The common cause is when the OS X EFI isn't selected in startup preferences (and then stored in NVRAM) so the system needs to read all drives before defaulting to the lowest numbered Mac volume. 

A more oddball case would be if the kernel caches are somehow invalid and must be recreated which slows a boot sequence considerably.