Solaris 10 releases up to and including Solaris 10 8/07 ("S10U4") incorrectly detect newer Intel processors produced since 2007. This problem leads to the 64-bit Solaris kernel hanging or crashing almost immediately during startup, in both virtualized and physical environments.
The recommended solution is upgrading to at least Solaris 10 5/08 ("S10U5"). Alternative solutions include forcing Solaris to always boot the 32-bit kernel or applying a patch for bug 6574102 (while Solaris is using the 32-bit kernel).