Inu dobrá, toto jsi už zkusil? Ps. první odkaz.

1)Restart Steam

Please completely log out of the Steam client (make sure it is not running in your Windows Taskbar) and then re-start Steam. This should correct the issue.

2)Move Steam

If the issue continues and Steam is installed to a location containing letters or symbols not contained in the English alphabet (such as accents), please move your Steam installation to a directory that does not contain these characters, such as C:\Steam. Please see the Moving a Steam Installation article for instructions on doing so.

3)Windows Vista/7: Repair the Steam Client Service

The Steam Client Service is a required component of Steam on Windows Vista and Windows 7. If the Service is not operating properly, certain Steam functions may fail.
To repair the Steam Client Service, please do the following:
Click Start button, then 'All Programs', and 'Accessories'
Right-click on Command Prompt and then click "Run as administrator..."
In the command prompt, enter the following command, including quotation marks: "C:\Program Files\Steam\bin\SteamService.exe" /repair
Note: C:\Program Files\Steam\ is the default installation directory for Steam - change this to the correct directory if you installed Steam to a different location. 64-bit systems will use Program Files (x86) instead of Program Files.
This process will take a few minutes to complete. Once finished, the message "Steam Client Service repair completed." will appear.
The issue may be fixed at this point, however it is recommended you reboot your computer before testing if the repair resolved the problem.