Ruffnutts, how are you starting swap? The log you posted looks to have an extra space in the command:
swapon: ../../ .swap
There's a space between the second / and the .swap which is wrong, if that is actually part of the command or script that you are using. Since the error message is "invalid argument" I think that an extra space has to be the problem.
If you have the .swap file placed in the root of your SD card (as per the example given elsewhere) then the easiest way IMHO would be to call it with swapon /boot/.swap and make sure you don't have any extra spaces in there.
Anyhow, either remove the extra space or use the full path/file rather than a relative one, and see if it works.