This can be caused by one of two issues; 1 - Your maximum connections have been passed programatically, this is not very common. 2 - The more normal reason is that your close connection + dispose is not being called, this leads to the same sort of error. IMO the best way to handle this is to keep the scope local and ensure correct handling of errors etc guaraantees that your connection is always closed and disposed of when it is no longer needed and then the connections goes out of scope as your function or sub is released to the garbage collector.