I often use the method of marking some text with the mouse and then holding down the ctrl key and dragging to a nearby point to copy the text (a standard Windows function supported by most apps), but that no longer works in 5.01. Now I have to start dragging the marked text and then press the ctrl key to switch to copy mode, otherwise if I hold the ctrl key down as normal and then start dragging it just extends the text marking. I've looked through all the settings but I can't see anything that might affect this. Is there some new feature I'm missing, or is this a bug in 5.01?

probably it's a side effect caused by Ctrl+Click shortcut for Find Declaration introduced in 5.0.1.

Does that mean it will be fixed in a future release?

it is fixed in 5029 and this build will be available shortly.