WeBuilder 2014 version 14.0 (14.0.0.184) - but this also occurred in previous versions.
If I manipulate a very large file i.e. 100,000+ lines WeBuilder can hang.
Opening such a file is usually okay, but editing it, or trying to delete its contents will often result in the application hanging.
To replicate this, open a very large file, select all CTRL A, followed by delete.