Assuming you are using a text editor (such as Notepad on Windows) and that entries you added are valid, the "corrupt VMX" error coud mean that an entry or several entries presumably pasted in at the end already exists. In this case, tools.syncTime or time.synchronize.tools.enable might already be there. Anyway, check the existence of every entry instead of just doing a simple copy/paste to the end of the vmx file.

The order in which the entries appear does not matter.