I've just finished some changes to the native foobar2000 0.9 audioscrobbler plugin.
Caching should work again with the new version. Also submissions are not aborted on seeking - your track still gets submitted, as long as the submission parameters (50% or 240s) are fulfilled.
Happy scrobbling!
Download foo_audioscrobbler 1.2.8
Edit: updated to 1.2.8 because I've identified another problem with caching.