I actually just noticed this myself today...and I am on a Lenovo T400. I looked at the On-Access Scan statistics and noticed it is just cycling through a folder on the C: drive called SWSHARE. From my understanding, this folder is used for Rescue and Recovery. I opened task manager and in addition to McShield, there was a process running that started with "tvt_" and would be second in CPU usage behind mcShield. This is the rescue and recovery service (from what I read, this keeps the current system state and the backups for recovery in sync). After stopping this "tvt_" service, McShield usage drops off almost completely. I am still looking for a workaround besides uninstalling rescue and recovery. Let me know if you find anything!
This sounds like VSE is behaving as designed. If a process is accessing a large amount of files on bootup the mcshield service will want to scan those files.
You could exclude the folder entirely. If you don't want to do that then alternatively you could setup low-risk process policies and add the process in question to the low risk process policy. Then disable scan on read/write for low-risk processes and that would also take care of it.