Sudden Envelope Weirdness

Greetings All...
Based on what I've seen here, envelope problems are old news. I've used Cakewalk since PA9. NEVER had a problem with envelopes. Yesterday,
I opened up a project that I last looked at a month or so ago and begin tweaking the volume envelope on the vocal. If I drag a node up or down
and let go, it immediately draws a dotted line(jump mode) to the next node and sometimes the node I dragged jumps back to where it was when I
started the drag. Other times, it deletes the node I'm dragging. Finally, If I move an entire envelope, it deletes the entire track. If I go to 'Undo'
on the menu, it says 'Undo Delete'.  This all happens globally on any project new or old. I must say I've never seen this behavior before. I am currently
on S7. Any pointers would be appreciated.

Thanks,

John