J-Link Error-pfcExceptions$X ToolkitCantModify

Hi i am trying to connect via J-Link to a running session of Pro/E with the following code:

System.loadLibrary("pfcasyncmt");

AsyncConnection connection = pfcAsyncConnection.AsyncConnection_Connect(null, null, null, 20);

but i always get the following error:

Exception in thread ;main; com.ptc.pfc.Implementation.pfcExceptions$XToolkitCantModify at com.ptc.pfc.pfcAsyncConnection.pfcAsyncConnection.AsyncConnection_Connect(Native Method)

i've already checked all of my system variables, and they're all right, i can't get rid of it. Can anybody help me?