I have a problem...

Send by email?

Try rebooting your computer.. :)
Otherwise, send by e-mail.

It could be a frozen process. Shift-Alt-Delete, go into Task Manager, open the process window, look for Steam.exe, kill process, close task manager, and try again.

Rebooting also accomplishes this.

Did you try the Steam client itself?

Copied from a Steam Support message:

Please try the following:

Exit Steam.
Click Start > Run (or Windows Key + R)
Type inetcpl.cpl and click OK.
Click the Connections tab.
Click the LAN settings button.
Note: You may want to write down the settings currently found in this window if you need to undo these steps later.
If any items on this window are checked, uncheck them.
Click OK to close any open windows and restart your computer.
Now, launch Steam and test the issue.

Note: Steam does not support the use of a proxy server. If you require the use of a proxy server for normal internet access, it will need to be disabled or bypassed for Steam to function correctly.

Hope this helps.

just leave a message for the person who won the giveaway, and explain the situation, most probably he would understand :)