This error occurs in a situation like the following:
Type :
Tclass = Class of Tobject;
Var C : TClass;
begin
...
C.free
Free is not a class method and hence cannot be called with a class reference.
Error: Only class methods can be accessed in class methods
This is related to the previous error. You cannot call a method of an object from inside a class method. The following code would produce this error:
class procedure tobject.x;
begin
free

Because free is a normal method of a class it cannot be called from a class method.

http://www.freepascal.org/docs-html/user/userse62.html