Does it work w/ Echofon on Firefox Rated 4 out of 5 stars

Does this also work with Echofon on Firefox?

Every time i click on the shorten link on FF 6.0 i get the warning message (in german): Firefox does not know how to open this adress....

The short link is not copied into the memory, but i can see it in my account.
Any solution for this problem?