FYI: Found a possible reason for slow startup / hanging applications tab on program start.
On a customer Thinkpad (i3 2350, Win7 64bit, 8GB Ram) it took CCleaner (5.07.x, also tested with 4.x) more than two minutes to become fully responsive and usable after starting it. GUI came up but "Analyze" stayed grey and whole app seemed to be frozen after a few clicks here and there.
Turned out the machine had about 1GB (!) pending crash report files in Firefox profile folder %APPDATA%\Mozilla\Firefox\Crash Reports\
After deleting the whole crash report folder content via Windows Explorer, CCleaner startup time was less than one second.
PS. What about adding the deletion of crash report files to CCleaner?
Actually the slow startup of ccleaner, in the way you describe, is almost invariably because the user (you) has a winapp2.ini file that is too large (not trimmed) and ccleaner is checking each program in the extended database for existence on the PC
CCleaner default install doesn't deal with the Crash Report produced by Mozilla products such as Firefox.
However I believe the winapp2.ini community file eluded to earlier in this topic does deal with them - of course you'd probably still experience the very slow initial startup and usage of CCleaner until the Crash Report files are removed.