I have a Grohe LadyLux model 33755 faucet. Last year it developed a drip that ran down the hot water line. I contacted a local Grohe rep who send me a replacement "mixing valve" that I installed in the body. This seemed to fix the problem, until today, when we discovered a drip running down down the hot water line again.

I had one of these and it kept developing leaks under the sink. I was calling the plumber and each repair cost more than a new cheaper faucet. I replaced it with a cheap faucet. It's been 7 years and no more leaks.

It looked nice, but...

This type of leak is easily the installation of the 3/8' compression fitting on the supply line connection. This brand and model are high end products not known for problems. Check that compression fitting for tightness first, no teflon tape needed. Grohe Product Catalog (http://www.grohecatalog.com/product/33755/)