Two accounts, same modem = can't find account?

Hi guys, i have a problem.

I signed up for whatpulse as “neytiri28” on my own computer.
Everything went fine, until I installed whatpulse on a second computer.
My plan was to create a second account so my sister can keep track of her typing on her own PC.

When I tried to pulse on her comp with her account, it didn’t wanna do it.
In the end I created a second account for her as I thought something went wrong with her first one. I could pulse then, but when I got back to my own pc I couldn’t pulse anymore. “Can’t find account profile…” etc etc.

I removed the program from my sisters pc and took a new username on my own profile (former name was “neytiri”, current one “neytiri28”) which meant I lost 16.000 keystrokes. Now I can pulse again, but I still wonder how come I was unable to pulse.

Is it because both pulses go through the same internet connection? Same IP number which gives troubles?

Thanks in advance

Oh, and I use version
Windows 7 Ultimate 32bit
No other extraordinary programs were running.