Thank you for the informations,
I 've never seen this, I will try to reproduce.
Could you please send me your logic project, and your aupreset of the oberheim.
Also what is logic version, are you using it in 64 or 32bit, what os version ?
I could not reproduce it with logic 9, the obsem 1.1.5 on two different 10.7.
I Let you know if I have more info.