Does the fact that a profit sharing plan has a requirement that a participant be employed on the last day of each quarter (allocations calculated quarterly) to recieve an allocation of an otherwise uniform formula make it a non-uniform formula and subject it to discrimination testing?? Any reference cite is greatly appreciated. Thanks.

I think you'd be out of the safe harbor and into general testing. IRS Reg. §§1.401(a)(4)-1©(3) and §1.401(a)(4)-2(b)(2)