I'm just attempting to narrow down the problem. Hopefully this will help Easypano to a quicker fix (Which I'm sure they will do). It most likely will be a patch to rectify the coding issue.
"If" it is as simple as some HTML coding it shouldn't take long I wouldn't imagine. Comparing the two (html) there are some differences.
To answer the question raised by Hoosier3D, I feel that you could open a TW3 project and republish with TW5 but you cannot go back once done. So, if you were to choose this - be sure to rename the project as soon as it loads and save as a copy.
Give Easypano a chance to issue a fix first.