> What did u mean by press 3 and 2?
This starts OS X with the 32-bit kernel. The following KB applies to 10.6, but there are reports this works with 10.7 as well.
[extracted from http://support.apple.com/kb/HT3773]
If your Mac uses the 64-bit kernel by default, you can start up with the 32-bit kernel by holding the 3 and 2 keys during startup.
With respect to the question above about Core 2 Duo vs. Core i5, the default kernel mode for Core 2 Duo is 32-bits. This explains why the Core 2 Duo has no issues, while the Core i5 must be forced to use the 32-bit kernel.
[extracted from http://support.apple.com/kb/HT3770]
These Macs use the 64-bit kernel by default in Mac OS X v10.6.
Mac Pro (Mid 2010)
MacBook Pro (Early 2011)
iMac (21.5-inch and 27-inch, Mid 2011)