I'm unable to boot centos 5.2. It starts and shows me menu listing, which means there is not any issue with grub.
Here is screen shot after starting server... it goes to prompt bash prompt instead of loading process.
I was about to say it may be an issue with initrd, but looking closer, it appears that you are booting to the bash prompt instead.
So it looks like it is jumping into single user mode by default. In that case, run:
(for multi-user network access)
(for multi-user network access with GUI)
if you can boot to either one, I suggest you look in /etc/inittab and make sure that it boots to the appropriate multi-user level by looking for this line:
EDIT: I just realize you are booting with init=/bin/bash, which meant you are bypassing /etc/inittab. In fact, I was able to reproduce it by adding init=/bin/bash within my Centos VM.
Restart again, but this time, remove init=/bin/bash.