Java Database Connectivity (JDBC)

I have an application that uses a JDBC thin driver to connect to an established development database. This application has been running fine for the last few months. It fell over during processing in the christmas period and now I am unable to restart the application due to a invalid username password error. The puzzle relates to the fact I have no problems connecting using sqlplus or toad using the same username password combination but trying to use it to create a JDBC connection always fails. I am at a loss to explain why I receive this error.

I have created a simple java class to connect the database that works with the production database and other databases located on the same server but connecting to the development database always fails with the same error.

FYI is also experience the same error when trying to login using other valid users.

Has anyone else experienced this type of problem, am I missing something?

Any help would be appreciated!