Recently, I noticed that the timeout values differ on CentOS v5.x and RHEL Linux 5.x guests on VMWare ESX4 and ESX3.5. I've notices that older ESX 3.5 set a 60 secs timeout and ESX4.x set to 180 secs. Luckly you can fix it easily:
# vi /etc/udev/rules.d/99-vmware-scsi-udev.rules
RUN+="/bin/sh -c 'echo 180 >/sys$DEVPATH/device/timeout'"
Find timeout value (180) and change it as per your requirements. Make sure you install the vmware-tools RPM.