Jamie,

>This has been going along fine for 12 months + until a week or so ago when then WC app has suddenly starting acting strangely. Sometimes the WC app isn't seeing data that is there in the DB...

Did something change 1 week ago? Are you running in COM mode or File mode on the WC app? If COM, did you (or someone) recompile recently and perhaps get the COM server set to "Multi-Use" instancing instead of the required "Single-Use"? (Check Servers tab on the Project - Project Info Menu with the project open).