The random crashes have finally been fixed.
I had been trying various things but just couldn`t figure out where they were happening. So i took a few days off from coding to clear my head and decided to start searching for the bug from scratch (previously thought that it had something to do with loading in levels). I started at the beginning of the code and followed it through manually to see what was happening and where it was taking me to, i eventually got to where the new levels were being loaded, but instead of taking me to the beginning of the main game loop the code was starting half way through the loop, which was ok for a few levels but eventually the crashing would happen.
This has now been fixed and i can now play the game from the first level right through to the last with no crashes( i cheated of course, so have to turn off unlimited lives for final release :-) The game isnt that easy).
I now have a few things to sort and a lot more testing then i can release game before the end of the month.