It's definitely your mods, installed any recent ones to cause this error?
I'd suggest you do like me, re-install your game or if you're using custom.img - simply remove all mods from it and start over. Every time you install 2-3 mods, go in-game and test it out if you'd like to avoid these issues in the future.
You should use a original gta3.img and add a mods one by one, this op-code warning is of vehicle mods; the mods must have
( .dff and txd files ) but some of the mods doesn't contain dff or txd, so if any of these two files misses you shouldn't install the mode, they will give you a crash, but! sometimes it will crash your game even if the mode contains both files(dff and txd), it's about your FX Quality.