the problem: sometimes when you startup the weblogic servers you may receive something like this:

-OR-

the solution: this is usually an indication that your data source may be setup incorrectly. HOWEVER, if your database is setup to display a security banner set by these parameters in sqlnet.ora

then this is a known bug causing the issue you are encountering. Search for bug 12582023 in My Oracle Support and there is a patch you can download to fix this.

Of course alternatively, you could just disable the banner on from showing up which should also remedy your connection issue.