A quick Google search found at least one case: Can't have multiple statement handles on a single database handle when AutoCommit is OFF at /usr/local/lib/perl5/site_perl/5.8.0/sun4-solaris/DBD/Sybase.pm line 105

Apparently this is because "DBD::Sybase silently opens up another database handle for you when you try to use multiple statement handles concurrently from a single database handle." <a href="http://www.cwinters.com/programming/yapc_dbi.html">*</a>