cut all history.xml files and paste them to another folder as a precautionary purpose.
Also check that you tns listener started or not
you can check it by giving command tnsping your_tns_listner_name ie your connect string. if it is not running then
start the service and try again by opening the sql developer
if still problem exists then delete your sql developer folder in
C:\Documents and Settings\sbutta\Application Data\SQL Developer\
of your user profile and run sql developer again
if this post helpful or correct please mark it . this will be beneficial for others like you and people will have interest in answering questions.
Edited by: Askdineshsinghminhas on Jan 10, 2013 7:09 AM