"Error reading response: missing /prtg"

The problem seems to start when i run a sheduled autodiscovery on 3 hp procurve switches, And the problem goes away when we reboot the prtg core server, (witch we don't want to do)

What PRTG Version are you running exactly?

We do know this error message and we can explain it for vmware and soap, but we can't explain it for wmi. Is it maybe possible that your wmi sensors do show a different error message?

Please install dotNet 3.5 next to dotNet 4.0 and install the windows updates for the dotNet Frameworks. Does it work now?

If this doesn't help please open a command prompt and change the working directory to the "sensor system" directory within the prtg installation directory. Then run the following command and send the result to our support team.

SipOptionsPingSensor.exe -ip=[ip] -port=[port] -user=[username] -pw=[password] -timeout=5 -retry=5

Please replace the placeholders in [].

we are running 13.1.2.1463 all .net 3.5 and 4 is installed and all their updates aswell.

will update prgt to 13.2.*.* shortly (waiting for the all clear from the tech's first)

will the error stop when i update to 13.2.*.* on the soap sensors? or is that another problem i will have to adress first?

(will run the command and send the results to the support team when I have updated and started autodiscovery again, i removed all autodisc so we won't get bogus alarms all the time)

We don't know if the update will fix your problem. There are a lot of bugfixes in the latest version, but to know more about your problem, we'd need to get the output of the command, we described earlier. Did you already send it to us?