Jeff's post indicates newer ones are laser-guided ... perhaps the old ones were wire-guided?
Even though it is the best MBT around, the orginal design of the Abrams body and armor is aging and enemies have had a long time to work the problem.
From the reports, at most they only have a few of them...let's hope that is the case and we can prevent them from getting more.
I defer to Jeff's expertise on this.