in addition to comments from mwlong and Maria Garcia, I recommend to share local log in this forum. You can obtain it directly from Exception dialog, click on "See detailed local log..." text.
Probably more than that will be required…
It appears the following Defect was raised by Maria Garcia for our development team to investigate your reported issue. This has been approved for a fix in a future release but a version for this has not yet been provided.
Defect 1104665: Item Types not…
Alessandro Rubini said:It was my first time using the B communities.
In such case, I recommend: