Timeout...obtaining a connection from the pool (1 reply)

I have been having this issue for quite some time and it's driving me bonkers. I recently changed some configuration parameters on our MySQL database server to hopefully stop this from happening, and it did not help. Every once in a while when someone does something repeatedly (like Log in to school account, submit invoice, log out, log into different school account, submit invoice, logout, over and over), I will then get this error:

MySql.Data.MySqlClient.MySqlException: error connecting: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

The database is on an Ubuntu Linux server. The application is on a Windows Server 2003 server. I recently changed the database configuration:

innodb_additional_mem_pool_size=512M
innodb_log_buffer_size=8M
innodb_buffer_pool_size=256M
innodb_thread_concurrency=0

This is similar to settings I have on a Windows Server that is working perfectly.

To fix this problem, I have to recycle the memory pool in Windows IIS, then it works well for a while until someone does this again. Any ideas?

Thanks,
Jesse