If you connect to a windows 7 computer with remote assistance then you may encounter a black screen during UAC prompts. Below is the fix for this problem.
Computer Configuration (Enabled)
Policies
Windows Settings
Security Settings
Local Policies/Security Options
User Account Control
Policy Setting
User Account Control: Allow UIAccess applications to prompt for elevation without using the secure desktop Enabled
User Account Control: Switch to the secure desktop when prompting for elevation Disabled