Recently we had an intermittent issues with lists.asmx. It was giving us SoapServerException as below:
Method not found: 'Microsoft.SharePoint.Utilities.SPChunkedStringBuffer Microsoft.SharePoint.SPListItemCollection.GetXmlInternal(Boolean, System.Collections.Hashtable, Boolean, Boolean)'.
The issue was occurring infrequently. We located the issue on two WFE machines.
The exception was saying "Method not found." This is little weird as how OOB dll file miss this method and what is the DLL it is referring to.
I opened the lists.asmx and found that it refers to STSSOAP.DLL.
I searched for the DLL file and we located at two different locations : 1. SharePointRootFolder\ISAPI 2. WebApplicationVirtualDirectory\_app_bin
While browsing through these directories I noted that the DLL files have different "Modified Date". We checked the other WFEs and this difference was not present there. The both files had different versions as "14.0.6024.1000" and "14.0.6122.5000". We recently had server patching and somehow this web application _app_bin folder had the old file and using it.
We replaced the DLL with latest version and the issue is resolved. :)