Trying to compile linux 2.6.38

Hi All, I am trying to compile (from the ubuntu 11.04 source) But getting this error message ? /usr/src/linux-2.6.38/arch/x86/kernel/entry_64.S: Assembler messages: /usr/src/linux-2.6.38/arch/x86/kernel/entry_64.S:1544: Error: .size expression does not evaluate to a constant Any thoughts ? Cheers Ian