wow its 2014 and we are still having problems with the path variable. I have installed ERP 2013/2014 to do some development and testing of ERPLink and was getting the Launcher could not be found error. I tried to Google the issue, and even use Sage KB/Sage city to get an indication why the issue would occur. Unfortunately I could not readily find an answer however a thought dawned on me and I decided to look at the path just for giggles and of course it was well over its usable limit. The biggest culprit was crystal reports/business objects. I resolved the issue by creating a new environment variable for CrystalPath and copied all of the business object path parts into the new variable. I tacked ;%CrystalPath% at the end of the Path variable and now ERP 2014 client opens and runs as expected.
Make sure you check your path if your having load issues with the client after an install!