After fresh install of 126.96.36.199 with JDK on XP a user is getting the following and cannot create any connections.. I would think this might be a classpath error of some sort but I dont know how to fix that... Multiple other users have installed this at our site and have not recieved this error only one person.
If you do have a pre-11g client it might be interfering. If so, you can try tricking sqldev by changing your ORACLE_HOME within a batch file inside sqldev's install folder. This would force using the supplied thin 11g driver: