O.T. Problems with Cubase sx 3

["Luigi Meloni" <luigimeloni74@libero.it>]

Hi everybody, I've installed Cubase sx 3 and am having some strange 
problems
with midi vst synths. I know that it is O.T., but since I use the computer
syncronized with an echoplex and a repeater...:-D
The problem I have is that if cubase is in play I can use the various 
synths
without problems, but when I put some tracks in record, the midi signal
enters the computer (I can see it from the leds on my soundcards, a 
terratec
phase 88 and a Audigy 2 Zs, but I can't hear anything and, most of all the
track does not get recorded. Absolutely no problems with midi in Cakewalk
Sonar and other softwares. The audio gets recorded with non problems, the
problem is only with midi VSTi (I use the Arturia synths and Halion SE).
Thanks in advance for the help
Peace 
Luigi