Advanced Java

Hi ,
i am using an application where we have a UI code and a Console application
user log in through UI and enter home page where he has two options upload and refresh. with upload he can upload a file and contents of file are displayed in UI in a table.the file content is inserted into database with status "new".console application is continous running process it checks into db if a file has status of "new" and picks up that file. processes the file and checks its contents if there are any discepancies it sends an email and status is changed to error or complete according to situation. But problem is arising when there are multiple users logging through UI when file is inserted by them at the same time the UI starts showing errors such as table not found.i have checked the logs what happens is after every file is uploaded a select statement is fired using prepared statement which is wrapped
around our application specific statement.it is gets closed everytime prepared statement is fired for two users it works fine but for third user it gives SQL EXception closed statement.