The (now 5) categories of income each have there own form 1116 and carryover. The categories are now passive (including most investments), general (including wages), 901(j), income re-sourced by treaty, and lump-sum distributions.
Suppose the deferred wages were taxed in Canada in 2008 (for the purpose of argument). On your 2008 form 1116, you report the tax on line 8, but only the wages taxable in the US on line 1a. (You will probably be audited as the tax might be greater than the income, but that is the proper way to report it.) In any intervening years in which you had Canadian general category income, you would have needed to prepare a general category 1116 to calculate the credit allowed and carryover.
Because of the special statute of limitations (code section 6511(d)(3), which you might need to bring to their attention), you can amend your tax returns back to 2005 to change the foreign tax credit calculations, or to change between electing the foreign tax credit or a deduction for foreign taxes. (Note that a recent court case determined that carrybacks, such as recalculated NOL carrybacks, cannot be carried further back. This is not binding on you, but it is indicative of the way the IRS and some courts will consider the matter.)
I think, to be more specific, I would need to know the amounts in question and what you filed on forms 1116 in the intervening years.