I wouldn't be at all surprised if it was the cream. I've had a few, shall we say, "episodes" after eating cream on a VLC diet...
It might also be worth taking a look at what sweeteners are in the jelly. I had a pretty **** severe "episode" a few weeks back after eating some sugar free jelly sweets. I *believe* they contained Malitol. I won't make that mistake again!
I've never had trouble with Rowntrees Sugar Free jelly, so I'm considering making my own sweets out of that by adding more gelatine to it to firm it up a little.