I have recently tried to install the 64 bit version of CentOS 5.4 on ESXi 4.1, but without much success. It stalls immediately after start (also in text mode) and all I got was a non-flashing underscore or dash. Several people reported similar problems. The general recommendation is to enable virtualisation support (VT) in the ESXi host’s mainboard BIOS. However, I had already installed other 64 bit OSes and therefore doubted this would help. Instead I simply tried CentOS 5.5 x86-64 and this immediately solved the issue.