This thread may be of some help to you. I have not read each and every message so far been posted under this thread, so if I am repeating some of these, please pardon me.
In my opinion, there is no set time frame that you can leave your sponsoring employer before or after getting your GC approved. I left my employer after working for him for 5+ years and a day before my GC approval, still was questioned throughly by USCIS. At the time of my interview I was really scared as I had not read up as much and wasnt as aware of the facts as I am now. The Immigration Officer told me that I could be deported, my GC revoked etc. etc. but that could just be a scare tactics also. the most important thing is that collect proof of why you left, make sure that your job description and responsiblities dont change (drastically at least). Again as long as you are prepared to defend your situation that you "had" to leave becuase of the circumstances or things beyond your control you would be fine. I believe USCIS looks for the intent and anytime you leave before getting your GC or immediately after getting your GC you are opening yourself up for that interpretation of the "intent".
Anything you do, just make sure that you inform the USCIS of your decision to invoke AC21 and decision to join another employer. In my case I had not done that (remember the day I made the decision to leave my sponsoring employer was a day before my GC was approved so I never felt it necessary), but I feel that, not informing the USCIS was the biggest mistake I made.
Hope this helps,
Good Luck
In my opinion, there is no set time frame that you can leave your sponsoring employer before or after getting your GC approved. I left my employer after working for him for 5+ years and a day before my GC approval, still was questioned throughly by USCIS. At the time of my interview I was really scared as I had not read up as much and wasnt as aware of the facts as I am now. The Immigration Officer told me that I could be deported, my GC revoked etc. etc. but that could just be a scare tactics also. the most important thing is that collect proof of why you left, make sure that your job description and responsiblities dont change (drastically at least). Again as long as you are prepared to defend your situation that you "had" to leave becuase of the circumstances or things beyond your control you would be fine. I believe USCIS looks for the intent and anytime you leave before getting your GC or immediately after getting your GC you are opening yourself up for that interpretation of the "intent".
Anything you do, just make sure that you inform the USCIS of your decision to invoke AC21 and decision to join another employer. In my case I had not done that (remember the day I made the decision to leave my sponsoring employer was a day before my GC was approved so I never felt it necessary), but I feel that, not informing the USCIS was the biggest mistake I made.
Hope this helps,
Good Luck