If using BWS + EET, the chapter checks for Boo's kidnapping were not patched properly until this week. Boo's kidnapping takes place during chapter 4 of BG2, but in EET (due to continuous chapter numbering), chapter 4 becomes chapter 16. The scripts for Boo's kidnapping were overlooked in the earlier EET patches (applied by BiG World Fixpack), so still expecting chapter 4.
1. Make a note of the current chapter number - use C:GetGlobal("chapter","global") to get the current value
2. Set chapter global to 4 with C:SetGlobal("chapter",4) for the duration of Boo's kidnapping (don't do anything else that would normally advance the chapter)
3. Restore the original chapter number (refer to the note that you made in step 1)