It is very unfortunate, that $comcall is far from stable in the current mIRC version. I really wish this was fixed, because I could make great things, but they often rely on $comcall, which at this point is almost useless for me.

Try this code, but beware it _will_ freeze your mIRC, forcing you to close it with ctrl-alt-del.

Code:
alias comcallbug {
  .comopen ie internetexplorer.application
  !.echo -q $com(ie,visible,2)
  echo -a Visible?: $com(ie).result
  echo -a Now using comcall to do the same
  !.echo -q $comcall(ie,myalias,visible,2)
}
 [color:red]  [/color] 
alias myalias {
  echo -a Visible?: $com($1).result
  .comclose ie
}