SQL & PL/SQL

While compiling a new procedure, I get an error message:
ORA-03114: not connected to ORACLE

Also, the listener.log states:
10-JAN-2008 12:21:35 * 12560
TNS-12560: TNS:protocol adapter error
TNS-00530: Protocol adapter error
Solaris Error: 130: Software caused connection abort
10-JAN-2008 12:22:10 * 12502
TNS-12502: TNS:listener received no CONNECT_DATA from client

This is strange because as I was writing the code I would compile after a section of code with success. The last block I added when I got the error works as a stand alone statement.

Then I opened a file that was already compiled on the server. Now, it is giving me the same error message. I know the code works because the compiled version is executed every night and there were no changes to the program.

We are on Oracle 10g and using PL/SQL Developer.

Any suggestions/thoughts?