I don't think it's a problem of too many plugins because I have only the default ones (no additional ones).
Please start it with -d form commandline to get the debug-output.
You might have to start C::B, go to the Code::Blocks debug panel in the logger-pane, close C::B and open it again, to make sur that you can see the debug log while starting.
I verified that when C:B hangs, the last line of the debug panel is
Caching internal gcc dirs for adding to parser...
After some seconds the following lines appear
Caching GCC dir: c:\programmi\MinGW\lib\gcc\mingw32\4.4.1\include\c++
Caching GCC dir: c:\programmi\MinGW\lib\gcc\mingw32\4.4.1\include\c++\mingw32
Caching GCC dir: c:\programmi\MinGW\lib\gcc\mingw32\4.4.1\include\c++\backward
Caching GCC dir: c:\programmi\MinGW\include
Caching GCC dir: c:\programmi\MinGW\lib\gcc\mingw32\4.4.1\include
Caching GCC dir: c:\programmi\MinGW\lib\gcc\mingw32\4.4.1\include-fixed
and C::B is ready to operate
To make sure it's a plugin, you can disable them all and reenable them one after the other...
I tried, and the problem is in the "Code Completion" plugin.
If I enable only this one the problem happens. If I enable all the others, the problem doesn't happen.
I don't know if this helps, but I have C::B on C: drive, and the *.cbp, and workspaces on a different logical drive (D:\), that is a different logical partition on the same physical drive as C: