Sybase ASE (linux) - Intermittent connection errors

My Linux box is setup with Sybase ASE 11.9.2-3 (same for the common files) and the openclient is 11.1.1-3. The server I'm connecting to is running 11.9.2.5. phpinfo shows sybase_ct support. PHP version is 4.1.2. I'm getting intermittent connection failures on various queries. Maybe 1 out of 6 times there will be a failure. Here's the error message: ----- ct_send(): network packet layer: internal net library error: Net-Lib protocol driver call to write data failed ----- Any idea what this means and what steps I can take to fix it? I'd hate to release an application that will have a 1 in 5 chance of failing any query. The machine connecting to the Sybase server is behind a firewall but I've opened port 2500. Maybe another port needs to be opened? Any suggestions would be appreciated. Jim