I have been having issues with Backup Exec as of late where it appears to go into this hanging mode and would run for hours while backing up Virtual machines. I had check our tape library to see if the drive were writing any data and from what I found out they were all idle.
Now we did not have this issue prior to updating to feature pack 5 and installing hotfix 115844 amd 116031. Furthmore, from what I understand feature pack 5 was suppose to resolve an issues with backing up Virtual machine that would cause it to hang which I had included the links below.
Lastly, according to the second article that I have provided it made mention of a delay catalog feature and for some reason it just disappear from our option menu. What I mean disappear is it was there and now its gone. I have check our other media server and I am able to see it.
I would also like to add the virtual machine that I am backing up does not have GRT enable by default. Therefore, as you can see from the previous image with the option "enable instant GRT" is something that I have not seen before prior to this issue.
The "delay catalog" feature was renamed in FP5. It is addressed in " What's new in Backup Exec 15 Feature Pack 5" as shown in the screenshop. You can open What's new dialogue in the BE UI (Backup Exec icon | Help and Documentation | What's new.)
You also may want to look at the vCenter or ESXi activity. See if it's taking a long time to remove the snapshot from a VM. Try separating your VMs to see if there's a specific VM that's causing the problem.