Same issue here as well. 

OK here's an update.... 1st I tried to reload my Proseries tax program - No help, 2nd ) I reboot the entire comp and reloaded the ProSeries  Program, That solved the invalid URL error! BUT, when I ran the Signature program afterward it came up with the what box but it was blank? no place to click next? heck no words at all? so closed everything down and tried again NOTHING same blank box. Then BINGO it came to me I run duel Monitors so I moved the Proseries program to the Main monitor and everything worked like it was supposed to. Hope this helps anybody having problems out there!