Hello,
I've found that under Windows Server 2003, the kpserver will not start if there is another (different) DICOM server already running and listening on the same port as K-PACS but with a different AETitle. Changing the port for the K-PACS kpserver seems to solve the problem and K-PACS and the other DICOM server can run simultaneously.
On Windows XP, however, the behavior I have seen is a different and more subtle problem. If K-PACS and the other DICOM server share the same port number (but different AE Titles of course), kpserver will run, but K-PACS intercepts data sent to the other DICOM server.
Aside from these strange behaviours, K-PACS is a wonderful program. Keep up the good work!