Error Message

[stuartwaring]

Hi All, I am building a campaign based around Lovecraft themes, so am bringing in the Great Old Ones from the Encounter Builder

One of the monsters (Tsathoggua) kicks up an error message I have never seen:

"Herolab does not support epic spellcasting at this time. Most of the effects of your current effective spellcasting level of 29 will be calculated as if you were Level 20"

What is odd is that lots of the other Great Old Ones have CL higher than 20 but do not cause this error.

Any ideas what ability is causing this and how I can get rid of the error?