Periodically dropped connection on clinets

[endx]

I'm experiencing a problem with Wingate 6.2. On clients I get connection lost each 5 minutes or so. I tried turning off checksum on the LAN card (that had such option) and setting to 0 registry value ValidateTCPChecksum HKLMSYSTEM\CurrentControlSet\Services\QbikHkXP\Parameters
but it didn't help.

I believe that on server connection drops too, because I constantly get "Connection lost" from eMule.