What was the error code you got? The steps to fix it depend on that.
mostly though, an eBoot should repair pre-boot issues.
There's no error code indicated instead it will search for a bootable device. I try to repair it but the problem is it will just stop during the winlogon/GINA then will prompt you again in the bootable device options. Was it okay if I use the decryption of whole disk then execute the restore MBR everytime this scenario happens? I want to know also if I can bypass the decryption process and skip it directly to restore the MBR.
restoring the original MBR won't help you get access to the data - it will just nuke the link to the pre-boot. So no, that's not useful.
If you get to WinLogon, there's nothing wrong with the MBR or the pre-boot - everything is working properly (except Windows).
So, if your BIOS thinks there's no bootable hard disk, as you say, something bad has happened to the MBR - any chance you've got a root kit virus? Not shutting down is unlikely to affect the MBR, as it's rarely (if ever) written to - EXCEPT if you have a root kit present which is trying to maintain persistence.
I think the hard disk is not infected of root kit virus and I do scan of it using VSE. I just read an article regarding what are the causes of MBR corruption and it says there are 3 different causes which are virus infection, drive failure or an MBR overwrite cause by a program. Based on FAQ of EEPC, the EEPC replaces the original MBR with its own code to allow pre-boot authentication environment to start. I just having a thought that maybe this could trigger to corrupt the MBR because it replaces the original MBR of Windows (if I'm not mistaken).
doubtful - EEPC can't function without changing the MBR so it does it very reliably.
Post the corrupt MBR - maybe we can tell what's replacing it?
Have you tried restore EEPC MBR then do eBoot ?
I believe the reason we can't just fix the MBR is the location of SBFS sector sometime moved (especially when there database update)
So keeping MBR copy for backup maybe useless..