This is not related to a particular instance. We can use TOAD and/or other SQL tools with no problem. This issue is very possible ralated to the microsoft security updates we did over the weekend. See the link for the miscrosoft updates.
http://www.microsoft.com/technet/security/current.aspx
After some Microsoft security updates over the weekend, the PL/SQL Developer starts freeze when I type . in the select statement. From example for the intended select statement:
select t.clientname, t.tractiondate from mytest t;
After I type select t. the PL/SQL developer will freeze...