Question:

I have a Craftman Riding 18HP, DOHC lawn mower, when cranking it starts up fine and idle supremely. But when I engage the transaxle [to move the mower] it stalls out and/or cuts off. Also, let me add, the riding mower was working fine a month ago, what could have happened? By the Way, while idling fine, if I engage the mower blades, it cuts off as well too. Strange huh? Thanks for your help in providing me a solution to my problem.

One of two things.
Is there a kill switch that must be engaged for the mower to run (usually setting in the seat or the clutch depressed, or the brake engaged until your setting on the seat).

Or it sounds like you have a belt or pulley that is engaged or frozen so engaging the drive stalls the engine.
My guess is the safety switch(es) are not turned off or are faulty

Yes, sounds like a safety switch issue, check the connections at the switches. Often they just need a little cleaning up to work again.