GOT IT!! How the dimmer works is that it only allows the power to flow for a fraction of a half cycle of the mains, let me explain:- The mains is an alternating sine wave, imagine the voltage smoothly going from zero to its max value then smoothly going back through zero to the same max value, but in the negative direction, it then reverses its direction and goes positive. This process continues all the time the power is on. If you don't know what a sine wave looks like, it could be approximated by semi circles sitting on the zero volts line, a positive going one followed by a negative one then a positive one. . .
The dimmer works by holding the power "off" during the initial part of each half cylcle the letting it flow for the rest of the cycle. So if the power is held off until the last, say 10% of each cycle, the actual power getting through is low, so the bulb is dim. If the power is let through right at the start of each half cycle the power flowing is at max so the bulb is bright. What is happening is that as the dimming level is reduced (bulb getting brighter) you actually pass the maximum voltage point, the CFL has a rectifier in it to turn the incoming AC into DC and this then has the maximum voltage on it and it charges up its capacitor to maximum voltage and hence the CFL goes to maximum brightness.
How to cure? Get different CFLs or dimmer
Frank ( I'll see if I can attach a diagram)