particle system caching/baking question - issues??

Hi there

I have a multi fluid particle simulation with around 160k particles which plays back fine takes about 12 hours first time through.
I can save the file and end up with a 1.2 gig blend file so I assume the cache is saved in the blend file?

If I go to bake the simulation it doesn’t work, the simulation bakes to a point and then the particles explode?
I have no idea why it will play back but not bake?
I’m probably doing something round the wrong way or missing something…

Any advice gratefully received.
I would attach the blend file but as mentioned it’s 1.2 gig…

thanks
Nigel.