The 2 out of 10 times it did work...did it work at all focal length or only at a certain focal length? For example if it worked at 75-mm to 100mm but you'd get Error 01 above that. If this is true, it is most likely that part of the electrical flex cable has broken off after repeated zooming. This is a common problem with Canon lenses.
Some people have successfully repaired this themselves with replacement part but it involves completely disassembly of the lens...a tough job for most people. I recommend sending it in for a repair quote...
