Microsoft informs that "A physical to virtual (P2V) conversion in SCVMM 2008 fails during 'Scan System' with error 2910. Job details show three separate errors under the Summary tab. Following this error, the P2V Agent isn't successfully uninstalled. Manual uninstallation of P2V Agent from the source system will also fail."
This can occur if the P2V Agent is unable to properly enumerate the App-V cache presented to Windows as a local drive; usually drive Q. This drive is visible in Windows Explorer but cannot be opened. This same enumeration issue prevents the SCVMM P2V Agent from being uninstalled.
"In order to remove the existing P2V Agent and perform a successful P2V of the Source machine simply uninstall the App-V Desktop Client. A restart is required. Once the drive no longer appears in Explorer the P2V Agent can be manually removed and a new P2V operation performed," explains Microsoft.
More Info: How to Uninstall the App-V Client