Default Data Source setting ignored

We're currently experiencing a minor glitch with RDM. I was using RDM with just two data sources on 6.1.3.0 previously, so I don't think it is an issue with this version, but now that I have my whole company running in RDM, we're up to 17 shared data sources (plus the default local data source). At some point (unfortunately, I don't know exactly when, since all the additional data sources were created during one day), though, the data source I have set as my default stopped being used as my default upon starting RDM. I've tried using a different machine and removing/re-adding all the data sources, but RDM is now always defaulting to the first data source (sorted alphabetically). Is there a workaround available for this? It isn't a critical issue, it is just a minor irritation, since unless you happened to want the first data source as your default, you have to change data sources as soon as you log in each time.