Version in portage is omnibook-20030828 and does not support 2.6 kernels.
Latest version on Sourceforge is omnibook-2004-01-20.
Steps to Reproduce:
Omnibook-20040701 is in CVS now; I don't have an omnibook to test it's functional but it compiles on both 2.4 and 2.6 fine here. Therefore, please reopen this bug if you have any issues. Thanks!