I've successfully got from 4.5.5 to 5.0.18 without issue.
I've just run the 6.0.1 installer to upgrade to 6.0.1 and it seemed to go fine.
Now I'm getting a certificate error when I attempt to access the web client.
In firefox I get:
Peer's certificate has an invalid signature.
(Error code: sec_error_bad_signature)
I answered N to installing any non exisiting components this time
KP