If you log out and click on Contact Seller the error message is missing the registration link so the second sentence does not make any sense. The phrases varname "mustreg" contains the word ^regcode which is what is being dropped from the sentence.
My suggestion would be edit the phrase and replace regcode with regtext
Do I insert the character ^ before regtext? What exactly does that character do anyway? I don't think I've run into it's use in database fields before.