I don't seem to get the reason why Gen.Yamir(Umpani Leader) attacks me after he briefs me for the last mission. I did what he asks me to do and I completed the missions he gave me. I escorted the umpani who was held prisoner at Bayjin with no problems. I can't understand his actions.

The hostility of Gen.Yamir starts after our conversation ends. Gen.Yamir gives me the reward of 300000 exp for bringing the umpani prisoner back added with the reward of the umpani soldier of 100000 in gratitude.

What bothers me most is the fact that Gen.Yamir is friendly to me and wishes me well on my last mission to destroy the T-rang transporter. There is no hint that he will attack me.

What went wrong? Was it a bug or a glitch? What do I do now?

should be a glitch, did you ally with the trang as well? try paying he'li a visit. if all fails, try reload a save game.

Hmm, I've never had this happen. If you paid Heli, then most likely completing to many T'rang quests before doing the Umpani quests is the reason. (sniff, sniff) I smell a game trigger here.