Product not appearing on front page

[Simmo1]

I use the combinations generator and due to the high multiplication count i usually only generate 1 product ans imply allow orders on the info tab. I am having problems of late entering new stock. Whilst it appears in the backend the product refuses to appear on the front end of my site. It appears as a white screen only with the surrounding templates on the outside.
The multiplication on these few itmem im having trouble with is 2280. Is this the problem? I.e. is the count too high? When i enter half of the required combiniations it works o.k.
The second problem i am having is when i need to change the generator combos it can take anything up to a minute to appear on the screen once hitting the 'combinations' tab. I can live with that however a few items of late they have not come up at all, resulting in me having to completely wipe the product and make from scratch again. I.e. if i cant change the combinations then the product is of no use to me.