The issue may be due to your MSDOS.sys file having the following setting:
The [Options] section can contain the following settings.
BootSafe= Boolean
Default: 0
Purpose: A setting of 1 forces your computer to boot in Safe mode.
Try editing thisfile with notepad to see if this is the case.
The issue may also be due to the Video Card driver. When in Safe Mode remove the listing under Display Adapters in the device manager and restart. Make sure you have the Video Card Driver handy at this point, for reinstallation.
You may also want to try removing any redundant and/or obsolete device entries in the device manager. This procedure can resolve Windows conflicts by removing redundant and/or obsolete device entries that are installed in virtual mode.