I regularly use Notepad++'s TextFX features to 'hide lines with clipboard text', select All, and then 'delete invisible selection'.
From time to time, the 'delete invisible selection' starts to take a long time, though it still works. I 'fix' it by reinstalling Notepad++ whenever it starts happening. Recently, however, it is happening much more frequently and I am having to reinstall the software every day rather than once every few weeks as in the past.
Windows7 64 bit, using shortcuts Ctrl+Shifrt+H for 'Hide lines with clipboard text' and Ctrl+Shift+DEL for 'Delete invisible selection'.