Could you try portable version because that's what I use. This behavior is rock solid consistent on all notebooks I tried so far, just checked Thinkpad T410 (1st Gen I-core) in addition. Do you have v 2.16 archived somewhere for comparison? Because if not I can give you this one. 2-3 seconds of lag versus instant should be noticeable.
EDIT: just checked, standalone version shows same slowdowns at initialization drives on launch and on NO DATA when switching those in GUI. I really hope you could compare this behavior with older version. If you don't have one I can give uploaded 2.16 (clean and no .ini) but will understand if you won't risk using it though. https://mega.nz/#!dQZg1LxR!gWLOmaar-AWdiPHS5bUaMnppxK5abkZvPuQgan0zzsw