Greetings
Trying to boot ubuntu 8.04.1  kernel 2.6.24-21-xen xen 3.2  leads to CPU 
panic.  BIOS has 2 options concerning Intel VT - Auto and Disabled . 
With disabled set everything works fine exept HVM domU support . After 
setting Auto option system fails to start.  bios flashed to latest version .

Hardware  Original description:
1x Dual-Core Xeon 1.6 GHz/1066 MHz (2x 2 MB L2 cache), 2x 512 MB 
PC2-5300 ECC AMF DDR SDRAMs, 0x 0 GB SATA HD (open bay), 48x CD-ROM, 
Broadcom 5721 KFB3 Gigabit Ethernet, ATI ES1000 (16 MB), 1x 670W power 
supply. In addition installed second CPU, 8 Gb DDr, Intel 5000P chipset
https://www-304.ibm.com/systems/support/supportsite.wss/selectproduct?familyind=5312474&typeind=5312476&modelind=5315615&osind=0&brandind=5000008&oldbrand=5000008&oldfamily=5312474&oldtype=5312476&taskind=2&psid=bm&continue.x=9&continue.y=17 

  Sorry for photos, no serial console cable.