This has given me a bloody headache tonight, but I was determined to try and solve this once and for all and have just spent the last hour figuring it out. Once I'd seen that you had the "UBBCode is disabled" it really puzzled me as to the right of the reply box it clearly says "UBBCode is enabled" so couldn't understand why it was disabled for you. As you can see, I had no problem in making the image in your last post displaying.
I tried checking if there was anything different on your account settings/preferences than mine. Nope nothing different. Tried resetting all the settings for this section (again), nope bugger all difference for your account. Then... I dug a bit deeper and found the problem. For this section (and a couple of others), a little box had been left unchecked to enable people on 24 month subscriptions to use UBBCode here. I've ticked that box now and you should be able to post in UBBCode here (and elsewhere) now. I think I've checked the settings for all the other sections, but I've missed any just post in here.

Incidently, this means I've also (finally!) worked out why certain people couldn't use the graemlins in here.