New to Java

Hi there;
It's been two days that i have been trying to fix this issue due , probably to its complexity.
I have written a web application that i managed to deploy and run using Sun Application Server 8.That was a week or so. Now i had to modify some details in my database, since i use an Oracle Db that i access through my web app.
The first time everything went fine. Now the problem is that i keep receiving the "sealing violation error" when i add ojdbc14. in my project library. But when i remove it, my app shows "can't import oracle.jdbc.pool.OracleDataSource".
Since i am sure that i may be wrong but something is not right here as well, i tried to write a simple program to connect to my Oracle db, without putting ojdbc14.jar in the project library and ignoring the "oracle.jdbc.pool.OracleDataSource" error that shows in the Ide. With this the project runs and the table is loaded. Surprisingly!
After some tries, and after getting back to the ide, i cant run the same program again. I made no change.
My classpath is fine with myoracle\...\ojdbc14.jar as well as my path.
I am using Oracle 10gR2. Could someone tell me what is wrong here? I have read some threads already about "sealing violation". How can I fix this runtime error? How can I import "oracle.jdbc.pool.OracleDataSource" without putting ojdbc14.jar in the project library?