if this is off the bike, you may be OVERLY hydrated. or you may be overconcentrating your drinks. try to cap the calorie count at 200-250calories per bottle so your tummy absorbs as fluid. when your tummy treats the drink as food it just sits there. try swapping whatever gel you use for something easier on the tummy. i prefer GU and in races have had substantial trouble holding down PowerGel and Carboom (ugh, esp Carboom -that was a disaster)
i've come to accept that i will cramp in the first mile off the bike. in time, i've just trained myself to run through it.
oh yeah, a good burp some times does wonders. yep, this thread is gross