Some of the problems people are getting with invalid addresses have been solved by click on the xc symbol and also clicking on the BLOCKNET symbol , you need to select >>>>input and output coins<<<< click the blocknet logo
I tried that and got this.
Invalid address2::Invalidaddress2::BMnA6f5SHGS93JJn3FhqfccmQADVQeDN5k:bitcoin:blocknetshares
looks like you trying to buy with btc from coingateway there . did you click on the coin you wanted to trade for, cos weird it saying bitcoin in the invalid bit