I opened a sequence in 3.5 and got this message.
. If you click OK several times it clears but the grid is blank. after it clears the grid returns and everything works as far as I can tell.
I have opened this sequence several time before this happened with no issues. I was working with the new beat track stuff trying to figure out how it worked.
I saved ,then opened the next day and saw the message.Capture.PNG