With todays integration build SWT has been broken into fragments based on windowing system.
With this change the location of the SWT jar and associated libraries has changed.
For standalone applications, when looking for the SWT jar or SWT library you can find them in the appropriate fragment ( libraries are in the fragment's "os" sub directory and jars are in the fragment's "ws" subdirectories). If you are setting the library path when launching your application you will have to change the value.
When running Eclipse within Eclipse, PDE will take care of finding the libraries and jars for you as before. If you have the SWT plugin loaded in your workspace and you update this with the new version of SWT you must get not only the plugin but also the fragment associated with the windowing system you are running on.