[T-Mobile Samsung Galaxy S II SGH-T989] RealPariah:
Should fix Shutdown Freeze

Hhhhmmmm, have you flashed any ROMs or was that a stock flash?

Even with stock flashes you can have issues just asking [for instance when I got a phone from Tmobile nothing would fix the shutdown menu not appearing for me then once I re-flashed a new ROM low and behold it worked].

Or if you are using the SmartAss V2 governor [or anyothers dependant on it like I believe lionheart is] in your CPU speed tweaking app you may want to use on demand or conservative instead. If you flashed any kernel, CPU tweak scripts you may need to check the values that applied [usually in init.rc folder somewhere as a script [just open in any text editor to read them]. Also definitely could be any UnderVolt settings [where you set voltage used by CPU under certain speed conditions and if set lower than the cpu can tolerate then when it switches to speed that is set too low is when it shuts off] . Undervolting can be done in either System Tuner or Faux Clock [swipe screen to left on open and viola global under/over volt setting :) ]. If you have not done any of these things or are unsure read below and see if that helps.

What I would try [in order]

First run backups in titanium backup and nandroid [titanium is so you can restore apps back without having to re-install and reset your settings and nandroid just to be safe if you are newer to working with Android Devices in this way]

Then Reboot in to recovery [on boot [right after you feel the very first vibrate] hold BOTH vopl keys in [press in center] and release when you see Samsung Logo, just be sure you release before it goes off screen]

Tap Clear Cache [in Main Menu]

Tap Clear Dalvick Cache [in advanced]

Flash Fix Permissions script [found in QA and in Dev threads for this phone] you want the Fix Permissions v2 by Minotauri zip [look at my past posts I have linked my mirror page to many posts]

You just save it to either internal or external sd and flash it just like you would when installing a ROM in cwm Recovery Menu

and reboot and see what happens [this should nail it really after clearing both caches and fix perms I bet]

if that does nothing reboot clear caches [if you had to wait to see] and go to mounts and storage and format /data [only]

Restart and see what happens...

If that really does nothing be sure to re-download your ROM via WiFi ONLY [or copy from computer]

be sure to flash darkside super wipe [google it, my mirror page, the forums, its everywhere] and Kernel Cleanser Script BEFORE YOU FLASH THE ROM

[Like So]

Boot in to recovery Flash Darkside Super Wipe

Flash Kernel Cleanser [another script [google, my mirror page, forums again]]

Then Flash ROM [and NOTHING else]

Boot phone [skip account setup we'll be back] wait 3 min after initial lockscreen if unsure] and don't do anything [no app installs setting adjusts nothing]

Restart in to Recovery again

Wipe Cache and Dalvick Cache

Install aany helper zips [like super user, toggles zip whatever with any custom radio being the last thing]

Restart Phone

You should not have shutdown freeze after reboot and clearing cache you should prolly still have it on initial boot, pull battery if needed and manually boot in to recovery as above.