I have this situation:
SONY VAIO SVF1521V1EB
Windows 8 preinstalled in UEFI.
I decided to install Ubuntu 13.10 in dual boot. So I downloaded the amd64 iso, burnt on a DVD, then booted from DVD in UEFI mode and installed Ubuntu.
It worked fine, I had Ubuntu and Windows 8 installed. On booting GRUB asked me if I wanted Ubuntu 13.10 or Windows Boot Loader (UEFI).
I used few times Ubuntu, and was ok.
Then I needed to boot Windows 8. I have booted it and worked a bit. Then shutdowned the pc.
When I powered it on, GRUB didn't appear anymore! It booted directly on Windows8 !
I reinstalled Ubuntu with the DVD and GRUB came back, then when I booted Windows8 GRUB disappeared again.
Does Windows delete GRUB? How can I have a "persistent" version of GRUB installed?
Thank you very much
EDIT: I tried all the workaround proposed, with no luck. I guess it is a problem in the VAIO firmware, which has strange settings about boot. PC manufacturers are worse and worse... They produce PC only for Windows, which I would not even define as an O/S.