Hello Maha, welcome to PharaohHeaven
Interesting question - and yes, this is the right forum for it.
With only 7000 people, you'd have had to have designed a horribly inefficient city to have hit the sprite limit, and if you don't have the whole map covered in small statues, you can't have hit the building limit either.
The only things I can think of are that you might have the burial goods bug (if you've dispatched all the grave goods before the pyramid is finished), but I haven't heard of this actually crashing the game, just corrupting the pyramid. This can only happen if you have the Cleopatra expansion pack, but not the patch. I suggest you get the patch if you don't have it already.
Or you might have the naval-battle bug. I can't remember whether Medium has naval battles, but positioning your ships in certain configurations during the battle can screw up your game. Try reloading from before any applicable naval battles and replaying them with a different strategy. That's all I can think of.
On another note, if you can't or don't want to use the straw you produce, you can turn it off in the overseer of commerce. Grain production will continue as normal.
[This message has been edited by WinterPharaoh (edited 09-28-2004 @ 06:06 AM).]