So, after grabbing BG2:EE and gave it one playthrough I couldn't help but miss the good old BG2 (modded, of course) with so many enhancements compared with the EE version. I decided to reinstall BG2, starting from scratch, with a selected number of mods.
This issue first poped up when a Planetar cast Improved Invisibility 10' on me when my HP drops low (I'm still in play testing, and haven't even biff'ed - I get like 0.5 FPS in game). Long story short, I found out the game crashes when Devas and Planetars are targeted by the Invisibility effect. The vanilla game does not have this issue.
The mods I have which affect celestials in some way are: P&P Celestials, 1PP, and Spell Revisions. P&P Celestials only affect their AI, or basically just what they do. Spell Revisions change their animations to those of human form - to take advantage of "attachable wings", and 1PP kind of makes them look "solid" instead of blurry like they used to be, with some color enhancements. I can get rid of this crash by changing their animations to human, as per Spell Revisions. Invisibility works fine on them when they're in human form.
In short, I like both how 1PP makes them look much better, and I also like the attachable wings - a lot, I might add. Obviously, I can have only one of the two: I can keep them either in solar form, or in human form with wings. So I thought I'd just point this out, to see if there's anything that can be done about this issue.
A thousand thanks to modders. Always have appreciated your work.
Currently installed mods:
1PP v4.1.0
Ascension
aTweaks v3.71
BG1 NPC SOA TOB v9
BG2 Fixpack
BG2 Tweaks
Divine Remix v7.1
Expanded Thief Stronghold
Infinity Animations
Item Revisions v3 Beta 1.1
Weimer's Item Upgrade v4.0
Lucy the Wyvern v4
Oversight v13
PnP Celestials v6
Refinements v3.31
Resource Fixer
Revised Battles v6.3
Rogue Rebalancing
Sword Coast Stratagem
Slandor & Lilacor
Spell Revisions
Tactics v25
Thrown Hammers v3
TOB Ex B0026
Unfinished Business BG2
Wheels of Prophecy
Wizard Slayer Rebalancing
I downloaded all of the above just in Dec 2013, so they should be quite up-to-date. Most of them I selected only 1 or 2 or a few components to avoid compatibility issues.
Edit: SOLAR animation does not cause crash. Only ANTISOLAR animation does. Also, the error message in ToBEx DOS window when the game crash is:
ASSERTION FAILED! Return Address: 0x9CCAD1 File: ChVidImage.cpp Line: 1910 Expression: !((dwFlags & CVIDIMG_TRANSLUCENT) && (dwFlags & CVIDCELL_BRIGHTEST)) Message: (null)