Okay, here goes: I didn't guard my cities in Egypt properly, so those stupid Bedouins took some of them (and of course, run away if you try to actively attack their armies in the field). The Mamelukes reappeared (I had defeated them) and were at peace with me. I sent an army to retake Cairo, but had to declare war with the Mamelukes again. The diplomacy window pops up, I check the declare war option, and NOTHING HAPPENS. So, I can't retake Cairo, which is a required settlement for the campaign, which means I can't win.
Later, I had the idea to let one of my provinces rebel, thinking a Mameluke army would try to take it. Unfortunately, it was the "Mamluk Rebels" who came calling, the province only reverting back to the control of the Mamelukes after the rebels had retaken it. I really don't want to restart my campaign, since I have everything else I need for victory, and just fought a terrific battle to capture Cyprus. Any help would be much appreciated.