I have to wonder how you are getting so much crime. There are three major points that can be made in general about this without knowing more about the specific situation, which may or may not be applicable to your games:
You should not build all the major crime producing buildings all over the place and if you do you should demolish some before you get to the point where major crimes start showing up (Control-A when in the city screen to get to the dialog where you can demolish buildings). Even if you want the special units that require this sort of building, you don't generally need more than one place you can make them. I rarely build most of them, some games I don't build any, and only 1 or 2 cities get the ones I do build (which is normally for the money, so they are built in gold specialized cities).
You should not keep the units that are made via the crime buildings in your cities, or even in your own territory if you can help it, since they are crime sources. You are supposed to put them in enemy territory to give them crime, not keep them around to give yourself crime.
Crime fighting units can get some free XP to start with extra crime fighting, allowing you to use fewer of them. Build them in the city where they get the most free promotions. The cost of having some of them in each city, even without much in the way of extra promotions, usually ends up being less than the cost of the crimes you get if they are not there, once the more expensive crimes show up, unless maybe you have too many crime producing buildings or are letting the crime units of other civs hang around you cities.
Oh, and a fourth thing: make sure you kill off enemy crime spreading units as quickly as possible. The AI will often try to move them into your territory. You don't need crime units of your own to see them (although they can), you need dogs. Roughly one dog unit per city is a good thing. Once the dog spots the criminal, use some strong combat unit with good odds to kill that unit (I generally like mounted units for this for the speed, especially before paved roads, but that is not really necessary).
Which kinda hijacks the thread. But...
After reading this thread I have tweaked Rocks to Rockets to increase the iMaxNumCitiesMaintenance in CIV4HandicapInfo.xml a little (instead of the various difficulties using the usual 4, 4, 5, 5, 6, 6, 7, 7, 8 they are currently at 5, 5, 6, 7, 8, 9, 10, 11, 12) which will hopefully trim down the excess gold situation in R2R a little. In R2R, much like C2C, I rarely have significant money issues that drive me off of 100% research for more than a few turns unless I start to expand a little too early or quickly when still on too many unfavorable civics. We shall see how much of a change this makes.