Thanks harknell,
I have looked at the memory limit, which is set to 20Mb, but i will try and use just one image in page to se if that works.
Support at my hosting site say that they think the problem is that mod_rewrite is being used, which they don’t support on a shared server. They can’t however find any errors on the server logs.
I thought from the wordpress docs that mod_rewrite was an optional requirement for use if permalinks were being used – am I missing something or is it used by default when using gallery plugins?