I got the last version of SQLDeveloper (Version 188.8.131.52).
When I execute a select , it's work fine but when i rigth click in the results panels for get the number of lines, it's hang always.
There is no response and the tool is unavalaible.
I use W7 whit the JDK of the distrib.
Perhaps, it's a bug ?
it's running a select count(1) from (select...your query here)
that query might be taking a long time to run