OK, it seems my W8 system is possibly in a bit of trouble...
I ran CHKDSK on my C: drive, and at the end saw this :
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Errors detected in the Boot File.
Windows has checked the file system and found problems.
Please run chkdsk /scan to find the problems and queue them for repair...
boot loop
boot record
chkdsk
corruption
diagnostics
disk repair
error detection
file system
mbr
mbrcheck
non-msapps
ntfs
partition
power cycle
refresh
ssd
system restore
troubleshooting
windows 8
windows image