Just recieved this,
I apologize for the trouble you have had with this feature. I can
confirm that this is a problem on the eBay site, and not with your own
PC. I have viewed your store and I see that it has the "&" symbol in
the store name. There is a site issue that is causing trouble with the
email marketing feature because of the & symbol. I know that sounds a
little crazy, but it is that symbol only in the store name that is
causing that error. We are working on getting it resolved, but in the
meantime, you can go in and change your store name and write out "and"
instead of using the symbol. You wont have any trouble with the feature
then. Once the problem is fixed, you can change it back.