From the Citrix website:
The GoToMyPC software is designed to work with the Windows User Account Controls (UAC) feature for the personal security of each user. If the User Account Controls are turned off, you may have problems sending the CTRL+ALT+DEL command to your host computer.
Turning User Account Controls On:
1. Click Start
2. Select the Control Panel
3. Select User Accounts
for Windows Vista:
4. Click Turn User Account Control on or Off
5. Check User User Account Control (UAC) to help protect your computer
6. Click OK
Note: You must restart your Host computer for the changes to take effect.
for Windows 7:
4. Click Change User Account Control settings
5. Windows 7 offers four different User Account Control Settings. GoToMyPC’s CTRL+ALT+DEL feature may not function correctly if the slider is set to the bottom setting, Never Notify. Move the slider up to select one of the other settings and click OK. We recommend at least the default setting.
Note: You may have to restart your computer for the changes to take effect.
You should now be able to send the CTRL+ALT+DEL command to your host computer. If you continue to have problems, your computer’s Group Policy may need to be configured to accept this command when it is sent remotely. Click here
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