The (unofficial) Milwaukie High School
forums are 100% stock on v7.7.1 and I do not have a missing </div> according to the w3c Nu Validator
; I also do not see this issue here at UBBCentral which is stock and running the current v7.7.2 snapshot.
If you remove the data from your HTML includes, does the error still display? Do you have any modifications installed?