Sending midi via ReWire to Cubase stops after a while

Hi,
When I want to send midi notes to Cubase 4 using ad_rewire I noticed the midi connexion between the two softwares stops after 3 to 8 minutes of good job. Sending 0-1 to hostcontrol~ stops working too.
However the audio sent by Max is still received by Cubase and the object hostsync~ still receives infos from Cubase.

Here is a patch that illustrates this issue :

My Max, windows xp, and Rewire driver, are updated. I tried this on several pc. With different versions of Cubase, and Max.
Is there a problem with my patch ? or is it another ReWire bug ?
If someone has an idea...
I am using a virtual cable instead, but that's a shame not to be able to use the sync possibilities of ReWire.