Hi Robert, thanks for getting in touch with us. That’s a strange problem!
If possible, could you try switching to a default theme such as Twenty Eleven and see if that helps? If it doesn’t, could you also deactivate all other non-Tribe plugins?
I’m guessing you are still in the test and development stage since you aren’t yet using a domain name, but if for any reason you can’t run through the above steps then just let me know and I’ll have a think and see if we can tackle this some other way.
I wondered also if you had customized your templates at all – the category view doesn’t look quite as I would expect.