I've been in a similar situation where pay checks were a month or so late. Eventually they showed up. Eventually we got more equity, but that equity was worth nothing in the end, as the company was "acquired" in a fire sale. I should've left and looked for a new job at the first sign of trouble (if not the second sign!)

Once you stop getting paid, forget about it: look for another job. It takes gross negligence to get into that situation in the first place.