Hi,
beside all the problems which are discussed here and which most probably arise due to false configuration of Mercury, I would like to state a successful update from 4.73 to 4.74 on a Windows Server 2003 R2 32bit. Update process proceeded without any errors (as usual).
The one and only conspicious thing which I have experienced is, that Mercury D (POP3 Client) is polling all of our POP3 accounts as fast as never before. It seems David has released all brakes. 
Greetings
Joerg