uhhh.. yeah.

If you have an error telling you there are too many animations, remove some.
If there's an Access Violation error, there are a number of reasons this could have happened.

• You have destruct/trigger/stomp/speed/bomb/collapse scenery events on a flipped animated tile.
• You have a textured background with at least one animated tile in it.
• You have Layer 4 set to Textured or Tile Width/Height.
• JJ2 just doesn't like you and is giving a random error.

Is it a popup error at all? Do you mean that some of the destruct scenery blocks don't work? That's because there are so many of those events. In Multiplayer, this won't happen.
Are there any start pos events? If not, you should put one in. It won't fault you in SP, but in MP, lack of start pos crashes JJ2.
Is it some other error altogether?