Hi Henrik,
I am attaching the screenshot of the pop up.
If I remove the output_format query parameter, the service returns the response in html and I don't get a popup.
here are soapui and http logs.
soapui logs
Tue Apr 30 00:20:06 PDT 2013:DEBUG:Attempt 1 to execute request
Tue Apr 30 00:20:06 PDT 2013:DEBUG:Sending request: GET /services/deployment/server/serverclasses?output_mode=json HTTP/1.1
Tue Apr 30 00:20:06 PDT 2013:DEBUG:Receiving response: HTTP/1.1 200 OK
Tue Apr 30 00:20:06 PDT 2013:DEBUG:Connection can be kept alive indefinitely
Tue Apr 30 00:20:06 PDT 2013:INFO:Got response for [deployment/server/serverclasses.GET serverclasses:Request 1] in 9ms (1657 bytes)
Autosaving Workspace
Tue Apr 30 00:20:16 PDT 2013:INFO:Saved project [splunkD-Demo] to [/Users/araza/QACode/soapUI-POC/splunkD-Demo-soapui-project.xml - 75573 bytes
Tue Apr 30 00:20:16 PDT 2013:INFO:Saved workspace to [/Users/araza/default-soapui-workspace.xml]
http logs
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "GET /services/deployment/server/serverclasses?output_mode=json HTTP/1.1[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "Accept-Encoding: gzip,deflate[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "Authorization: Basic YWRtaW46Y2hhbmdlbWU=[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "Host: localhost:8089[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "Connection: Keep-Alive[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "User-Agent: Apache-HttpClient/4.1.1 (java 1.5)[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:>> "[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "HTTP/1.1 200 OK[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Connection: Keep-Alive[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Date: Tue, 30 Apr 2013 07:20:06 GMT[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Expires: Thu, 26 Oct 1978 00:00:00 GMT[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Cache-Control: no-store, no-cache, must-revalidate, max-age=0[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Content-Type: application/json; charset=UTF-8[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Content-Length: 1657[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Vary: Authorization[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "Server: Splunkd[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "[\r][\n]"
Tue Apr 30 00:20:06 PDT 2013:DEBUG:<< "{"links":{"create":"/services/deployment/server/serverclasses/_new","rename":"/services/deployment/server/serverclasses/rename"},"origin":"https://localhost:8089/services/deployment/server/serverclasses","updated":"2013-04-30T00:20:06-07:00","generator":{"build":"160837","version":"6.0"},"entry":[{"name":"foobar2","id":"https://localhost:8089/servicesNS/nobody/system/deployment/server/serverclasses/foobar2","updated":"2013-04-30T00:20:06-07:00","links":{"alternate":"/servicesNS/nobody/system/deployment/server/serverclasses/foobar2","list":"/servicesNS/nobody/system/deployment/server/serverclasses/foobar2","edit":"/servicesNS/nobody/system/deployment/server/serverclasses/foobar2","remove":"/servicesNS/nobody/system/deployment/server/serverclasses/foobar2","applications":"/servicesNS/nobody/system/deployment/serverclasses/foobar2/applications","clients":"/servicesNS/nobody/system/deployment/serverclasses/foobar2/clients","reload":"/servicesNS/nobody/system/deployment/serverclasses/foobar2/reload"},"author":"nobody","acl":{"app":"system","can_change_perms":true,"can_list":true,"can_share_app":true,"can_share_global":true,"can_share_user":false,"can_write":true,"modifiable":true,"owner":"nobody","perms":{"read":["*"],"write":["*"]},"removable":true,"sharing":"system"},"content":{"blacklist-size":0,"currentDownloads":"0","eai:acl":null,"loadTime":1367304520,"machineTypesFilter":"","repositoryList":null,"repositoryLocation":"/Users/araza/Desktop/splunk-ds/splunk/etc/deployment-apps","restartSplunkWeb":false,"restartSplunkd":false,"stateOnClient":"enabled","whitelist-size":0}}],"paging":{"total":1,"perPage":30,"offset":0},"messages":[]}"