This is one of the many reasons I do not like cats...

If it were me, I would have a squirt bottle handy, full of water...  If you get caught hitting the cat with the water, say you were misting the iggy!! Can't argue with that! 

I also like bb guns, airsoft guns, duct tape (haha), water pans around cage.... (I can be creative, I dont like cats...)

scatmat
I posted this link in your blog, too.
I have several cats, several snakes and lizards, and so can empathize with your dilemma.
Squirt bottles only work if there is an operator on duty. Like they say, when the person is away, the cats will play! The scat mats work 24/7.
I do feel sorry for you that you not only have this behavior problem with the cats, but that the owners of the cats seem to be disrespecting you as well. They should at least pitch in for the cost of the mats, should you go this route.

I hear ya brother.

I wish I had an answer for you.  But, I'm in somewhat of the same situation with my sister's cats and the lizard enclosures in the livingroom.

Even though they seem to have backed down a bit(I've had to deal with her cats for the past 2 years).  They still seem to like to bat at the cages once in a while.  I hope maybe after a while your cats get tired of the iguana.  In the meantime, it can be a lot of stress for the iguana.

I hope you get better answers than I can give you....maybe it'll help with my situation too.

I'm actually moving in about a month. So I'm just looking for a temp solution for now. Two of the cats are coming with us though. Fortunately they're the cats that could careless about whats in the big green cabinet against the wall.

I have a cat problem also. i tried every thing but killing them. i tried the scat mat and they jumped over it i tried putting it on the cage and the batted at the front i took my lizard out and put it in another cage and put the cats in his cage and the tor the screen all to heck trying to get out i put them in another room for the day but they scrached the heck out of my door trying to get out. my sis dosen't listen and dosen't care what i say so she lets them out all the time anyway. i go to work before she goes to school and as soon a i leave she lets them out. im about to lock them all in a dog crate sis too. im out of ideas. i like the cats i dont like what they do. i cought them in my tort table to day while i was in the other room. im about to go out and buy a shock call for larg dogs. one that i can program so when they go down stairs where my reptiles are they get the crap shocked out of them. strong enough to knock their fir off or at least singe it a lil.

Oi. I feel your pain. I have 6 cats now (took in a stray last night we're keeping) and 5 of them are hellions when it comes to my snakes. I have to keep my bedroom door closed because they've cost me nearly $70 in repairs on the screen tops for the snake tanks. Not only that, but I now have 2 pet rats too. So if it's not the snake tanks, it's the rat cage. My cats, especially my cat, are beginning to destroy my bedroom door clawing it during the night.

Try those rubber mats with the plastic/rubber spikes, I'm looking into those myself, laying them ontop on the tanks and cage.

I have two cats but they really aren't much of a problem. I would suggest what great said, the scat mat is a great tool to keep cats off stuff.  The water bottle would also be highly effective however, I do think you should have some ability to keep your iggy safe and unharrased.  I'd have a little family talk about the situation.  Can you shut the door to the iggy's room. 

My cats don't bother my snakes in their tanks or tubs. They can't sit on the tanks in the shelving unit, and I put an empty wire rabbit cage on top of my gopher snakes' tub so they can't sit on that. The lizards are used to the cats and since the lizards are also in wire covered tubs the cats cant get to them. The lizards can't reach the screen top, either.
When I put my lizards outside on the porch for the warm season they will be in a couple of those 48x24x24 iguana screen cages, and then I will have to keep the cats from attacking the lizards as they scuttle around on the screen. My plan is to fence off the area containing the cages.

For awhile this winter I had them in the iguana cage indoors but it was too hard to keep them warm at night. This is just to show how I surrounded the cage with 2x4 inch welded wire fencing and bungee cords. I had also put a piece of cardboard on the top. When I set up the cages this spring I'm going to place them horizontal instead for more floor surface, and have a section of the porch cat proof (and raccoon and skunk proof, too!)