How can I import Contacts and Accounts at once?

I used to do this with the Contact Import Wizard but now it's not working, it doesn't let me import more that 50 contacts at once. (I already contacted support, it's a bug that "it's supposed" to be solved in the next release)

The Data Loader doesnt let me upsert both Contacts and Accounts at one time.

Any suggestions how can I accomplish this? I have several files a week that I need to import and this is creating a huge issue for me.