After looking at the logs myself (an uneducated look) it seems as if ESXi is mounting the file system (iso) properly but the vm isn't seeing the drive..
2012-01-28T17:03:28.769Z| vmx| DICT ide1:0.present = TRUE
2012-01-28T17:03:28.769Z| vmx| DICT ide1:0.fileName = /vmfs/volumes/4f23c632-b6d5f29e-70b0-000c2947a8c1/cucmiso/UCSInstall_UCOS_UNRST_8.5.1.12900-7.sgn.iso
2012-01-28T17:03:28.769Z| vmx| DICT ide1:0.deviceType = cdrom-image
Could there be something I am missing in the bios of the guest??