All right, I updated the SSP Pack, both for Native 1.153 AND Native Expansion.
Apparently v.1.153 of Warband included 2 new scenes, which was messing up everything.
The revised versions are available from the first page of this thread.
I tested the new pack with NE, and it was working.
Started a game in Shariz with no trouble.
If you do encounter troubles or glitches with the SSP, please report them !
@mike56: thank you for your answer!
Apparently v.1.153 of Warband included 2 new scenes, which was messing up everything.
The revised versions are available from the first page of this thread.
I tested the new pack with NE, and it was working.
Started a game in Shariz with no trouble.
If you do encounter troubles or glitches with the SSP, please report them !
@mike56: thank you for your answer!