Turbo 'too many users' error

Does anyone have information about this problem: We are running Turbo 2.10.03 on a 3B2. Several users can access the database simultaneously. After being up for several days, only one user will be allowed to access the database at a time; other attempts to open the database will fail with sqlcode -529, cisam code -129 (too many users). However, tbstat -u shows only a few users accessing the database, much fewer than the 100 defined in tbconfig. The problem is cleared by stopping and restarting turbo.