Too Many Distributed Transactions

Getting this error (ORA-02042) from an application running on an Ora8.1.5 Db (on Win NT4).

The app uses a DB link from DB1 to another 8.1.5 DB (DB 2). DB1 has a number of views created that retrieve data, via the link, from DB2. All the transactions occur in DB1. DB2 is used just as a data source.

Why then do we get this error? There are NO distributed transactions going on at all. There's nothing in the ALERT log and no trace files are generated in the user dump dest.

The INIT parameter DISTRIBUTED_TRANSACTIONS was set to 10. Checking when the error occurred, we had 3 online users and 5 transactions (all in DB1). I upped this to 20 , but why is the error occurring at all...?