Ona WMA lossy (320kbps CBR) track, this problem doesn't occur.
I have WinXP SP2, DirectSound output with:
[X] Enable hardware acceleration
[ ] Crossfade tracks
[ ] Fade in new track
[ ] Remove silence at the beginning / end of track
[ ] Smooth pause
[ ] Smooth seek
[ ] Smooth stop
EDIT: Originally reported in 1187, thought fixed in 1248, found present in 1256.
Steps to reproduce:
1 Clear Now Playing
2 Add to Now Playing two instances of a WMA Lossless track containing just 12s of sound followed by 8s of silence e.g. the file**
3 Click Play
4 At 14s on the seek bar, click the bar

Expected: playback seeks to 14s and plays the remaining 6s of the track
Observed: playback immdiately skips to the next track.
This on Win XP SP2 with Windows Media Format 11, MM 1256 with the following output plug-in selection and config:

Tracked at http://www.ventismedia.com/mantis/view.php?id=5967
** EDIT: ...that I tried to mail to support@mediamonkey.com but was rejected, so I sent as web support ticket TBT-894308 .