Connection Closed Errror

System

We are intermittently getting the following error (using WSMP4.1)

java.lang.RuntimeException: unexpected invocation exception: unexpected invocation exception: Connection is closed
*********** at com.imanage.cms.fc.cmsconnection.VirtualMethodInvoker.invokeMethod(VirtualMethodInvoker.java:115)
*********** at com.imanage.cms.fc.cmsconnection.ClientInterfaceVirtualProxy.invokeSingleMethod(ClientInterfaceVirtualProxy.java:150)
*********** at com.imanage.cms.fc.cmsconnection.ClientInterfaceVirtualProxy.invoke(ClientInterfaceVirtualProxy.java:106)
*********** at $Proxy0.trusteeSearch(Unknown Source)
*********** at com.imanage.cms.t2.jom.impl.LibraryImpl.searchTrustees(LibraryImpl.java:619)
*********** at com.imanage.cms.api.workteam.impl.LibraryImpl.getUserByLoginId(LibraryImpl.java:1257)

This is occurring when trying to invoke library.getUserByLoginId().

1. Can you suggest the reason for this error?
2. Is there a way to check that the library connection is still active before invoking any method? Something like Document.verify().
3. Is this related to the number of connections available?