Could somebody advice what's "ThreadSecurity error: rc=7" means?

I have installed RTC ISPF client 4.0M5a on z/OS 1.9 and server on windows. When I try to connect to RTC server, I got following error message:


# Time - Type - Port - Description
2011/Dec/27 13:05:14.596 - CONNECT - 4770 - Client connected
2011/Dec/27 13:05:14.609 - REQUEST - 4770 - POST /service/com.ibm.teamz.daemon.client.internal.IZFilesystemRestClient/Login
2011/Dec/27 13:05:15.247 - JSON_REQUEST - 4770 - Request, Progress-Key: null
repositoryUrl = https://10.0.140.222:9443/ccm
userId = TAP001
password = TAP001
timezone = EST5EDT
mvsId = SPMVS3
2011/Dec/27 13:05:27.102 - JSON_RESPONSE - 0 - Response (500)
{
 "errorClass": "java.lang.Exception",
 "errorCode": 500,
 "errorMessage": "ThreadSecurity error: rc=7",
 "errorTrace": ,
 "errorTraceMarshall": [
 {
 "errorTraceClassName": "com.ibm.teamz.daemon.client.internal.ZFilesystemRestClient",
 "errorTraceFileName": "ZFilesystemRestClient.java",
 "errorTraceLineNumber": 386,
 "errorTraceMethodName": "switchAuth"
 },
 {
 "errorTraceClassName": "com.ibm.teamz.daemon.client.internal.ZFilesystemRestClient",
 "errorTraceFileName": "ZFilesystemRestClient.java",
 "errorTraceLineNumber": 1922,
 "errorTraceMethodName": "postLogin"
 },
 {
 "errorTraceClassName": "sun.reflect.NativeMethodAccessorImpl",
 "errorTraceFileName": "NativeMethodAccessorImpl.java",
 "errorTraceLineNumber": -2,
 "errorTraceMethodName": "invoke0"
 },