Build #255 installation failed

I haven't updated my MMF2 for a long time and I've just tried to install the build #255. Sorry, this problem might have appeared earlier in the forums but I haven't found the exact solution:
I chose to use the manual registration. I pasted the manual reg. code I was given at the generated URL but then I got the message that the manual registration code has been expired. What could be the problem? Should I reinstall MMF2? This problem appeared when I wanted to install the iOS exporter, too.

Thanks for your answer,
Simon

Thank you for your answer, Jeff!
First of all I tried to generate the code on an other computer that has internet connection, but after that I managed to get internet connection on the pc that has MMF2 installed. I tried the manual registration, then the internet registration, but none of them did work. I got error messages in both of the situations.

As I wrote to Yves in another thread, my pc is really old and has not been maintained for a long time. There could be something wrong with my machine, not with the installer...
Thanks, I will try again (or I will try to reinstall MMF2).

Sorry, I think it was my old PC's fault. I installed my XP in VirtualBox on a Mac and it works seamlessly. Thanks for your support!
Simon