This error is described in PI SDK Help with the Server.Open method:
In general, when a PI-SDK application loses a connection to the server, subsequent calls that require the server will attempt to reconnect using the original connection method, however this reconnection mechanism is throttled. The Server object keeps track of the time at which a disconnection occurs. If reconnection is attempted either implicitly by accessing a method or property which needs server support or explicitly by calling Server.Open before the throttling interval elapses, reconnection is not attempted and pseRECONNECTTOOEARLY is returned to the call. Currently, the throttling interval is set to 60 seconds. This prevents applications from becoming unresponsive while the PI-SDK times out attempting to reconnect to the PI server. For details on automatic reconnection behavior see the topic "Reconnection" referenced in the See Also section of this page.
In addition to generic errors (such as Out of Memory), the following errors may occur:
ServerID in the Known Servers Table does not match that returned by the server. The connection is left open. This is an informative error indicating the clients notion of the server does not necessarily agree with the Server connected to. See the Servers.Aliases collection.
Unable to translate one of the supplied arguments in the connection string.
No global session manager was found. Fatal error.
Unable to open a connection to the server. More detailed information is included in the description field of the raised error.
Too soon to attempt reconnection. The PI server connection was broken and the retry timeout interval has not yet elapsed. This prevents excessive connection attempts to the server that may make the PI-SDK application unresponsive.
A Winsock error occurred while trying to open a connection. This represents a low-level communication error, possibly the servers network name is not recognized. The Winsock error number is reported in the description field of the raised error.
This is a generic access denied message and generally means improper login credentials were provided with the call.
Are there other errors possibly indicating why the connections was lost?