We have now placed a beta version of 4.0.2 on our download page for the more adventurous. We have been running the 4.0.2 code here on our support forum for some time without incident and believe it to be as stable as it can be but beta is beta so, of course, there may be the odd wrinkle to smooth out.
For a full list of the fixes and changes for 4.0.2 please visit our 4.0.2 Trac Report. This release contains mainly fixes to errors reported through the forums.