Before backing up to your destinations, the CrashPlan app performs data de-duplication. Large file selections take more memory to de-duplicate, so in some cases, a large file selection (over 1 TB or 1 million files) can cause the CrashPlan app to run out of memory and crash. Adjusting the maximum amount of memory allocated to the CrashPlan app service can resolve this issue.
Click the link below for more info.
http://support.code42.com/CrashPlan/Latest/Troubleshooting/CrashPlan_Runs_Out_Of_Memory_And_Crashes