I recently purchased Splinter Cell Conviction using Steam. I Preloaded it (which was a mistake….expanded on later) and the game did not work right away. In fact it took me a day to figure out how to fix it.

I first tried deleting the Contents in the host file. Everything WITHOUT a (#) was deleted and I tried again to avail.

Next I tried disabling all of the firewalls on my computer. That was no good.

Finally I after looking long and hard I figured out what to do:

What I actually had to do was uninstall the Ubisoft Launcher using Add or Remove programs and then reinstall it (letting steam do all of the installing). The game seems to get interfered by previously used games. In my case:
Splinter Cell: Chaos Theory
Splinter Cell (Original first one)
RUSE Demo
These are the only games I have on my system which are Ubisoft. Only one of which required a DRM, which I think RUSE  (DEMO) does.
Here is what Ubisoft Support told me to do. Just in case it may help you:
1. Some anti-virus or firewall programs may prevent the Game Launcher from communicating properly with the service. Please make sure that you have updated any anti-virus or personal firewall software you have installed. Some software may need to be uninstalled from your computer to play the game. Programs known to interfere with the Game Launcher:

 

ZoneAlarm
NetLimiter
Avira
Komodo
Hamachi

2. Are you able to access the following URL?

http://static3.cdn.ubi.com/orbit/satellitelist/satellitelist.txt

the resulting page should look like this:

216.98.51.199
216.98.51.201
216.98.51.202
216.98.51.203
216.98.51.204
216.98.51.205

If not, please let us know immediately and attach the three files requested below in item (4) to this incident.

3. This problem may have to do with connecting through a proxy server to connect to the Internet. The Ubisoft Game Launcher uses the Windows settings for the http proxy, but some configurations could experience problems. If you connect to the Internet through a proxy, please try the following:

- Locate the settings.ini file located in the installation directory of the Ubisoft Game Launcher (C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher)
- Open it with Notepad, and add the following at the bottom of the document:

[ProxySettings]
ProxyHost=proxyhostname:proxyport
OverrideProxySettings=1

You will need to change the proxyhostname and proxyport to the values setup for your proxy. You can USUALLY find this information by:

- Open Internet Explorer and go to Tools –> Internet Options
- Click on the Connections Tab and click on LAN Settings.
- The Proxy HostName (address) and Port can be found in this window.

If you don’t know this information or are unsure how to find out your proxy settings, you may need to contact your ISP or network administrator for more information.

4. If you continue to experience a problem, please send us all the .txt files in the launcher install dir:

On Vista/7 –> C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher

The files we will need are:

launcher_log.txt

orbitdll_game_log.txt