Usually because the original MQ4 file had errors in its code. If you have the source code open it with meta editor and fix the code where errors are found. Or it could be modifications made to MQL4 from Metaquotes updated software as Eelectric Savant said. I've had this several times from some of the EAs posted by hellkas with the files not loading into MT4 correctly. Still no point in keeping a thread alive that has no support or testing anyhow.

Thx waltini