CRM 2011 : The Sandbox SDK Listener failed to start. Source: CrmAsyncService.exe

uninstall the last roll-up (ex: roll-up 13)  and this will solve the problem.

Memory gates checking failed because the free memory is less than 5% of total memory

The easiest way just add this into your web.config

<serviceHostingEnvironment minFreeMemoryPercentageToActivateService="0" />

CRM importing error: you don't have the necessary permissions to change the domain login name for this user

The cause was that the crm application pool account needs read/write access to this folder on the CRM server.

C:\\Program Files\Microsoft Dynamics CRM\CustomizationImport