Windows Defender or third-party security suites frequently block or quarantine portions of the keygen's code mid-execution.

Using the wrong version of the activation tool causes immediate memory allocation failures.

Are you seeing this error , or does it happen while working on a specific drawing ?

: Temporarily disable your antivirus software. Sometimes, antivirus programs can mistakenly flag cracks/keygens as malicious and interfere with their operation.

C:\Users\ \AppData\Local\Autodesk\AutoCAD 2013\...\GraphicsCache

: Security software flags keygens as "Riskware," "Trojan," or "Malware." The antivirus will isolate or block the file's memory execution, resulting in an access violation.

: Enter standard standalone keys (e.g., 666-69696969 ) and the Product Key ( 001E1 ).