Problems running my web app live. No db connection. VWD2005

I created a web app using VWD2005 Express Edition adn uploaded my files onto this hosting server. I added a SQL database (and also paid to have that addon on my account) to my project which by default is stored in the App_Data folder which I of course also uploaded onto the server. However, when I test my app online (having tested it many times on my local machine successfully) I submit the form and the 'error.aspx' page I created pops up telling me the message that I had written on that page. Therefore apparently no conection was established and no entries were added to the db.
Any clues??? truly appreciate any help. Thx.