Memory can't be written E_FAIL (W7 64 host, Ubuntu 64 guest)

[sanitykey]

Hi, I downloaded the latest version of VirtualBox to run Ubuntu 64 bit on my Windows 7 SP1 64 bit machine. It sets up the machine fine, but when I try to start it the following happens:

1) If I start it and do nothing, it comes up with 2 errors, first is an E_FAIL (0x80004005), second is instruction at 0x10051890 referenced memory at 0x10051890 memory could not be written.
2) If I start and quickly select the Ubuntu 64 bit ISO to load from the VM loads for a second and then closes abruptly (probably the same error but it just doesn't show it except in the log).

- VirtualBox Version: 4.3.21 r97963
- Host OS: Windows 7 Ultimate SP1 (64 bit) Fully Updated (including KB3024777-amd64.exe)
- Host Memory: 8 GB RAM
- Guest: Ubuntu (64 bit)
- Guest Memory: 512 MB RAM
- Guest Additions: Oracle VM VirtualBox Extension Pack (Version: 4.3.20 r96996; VRDE Module: VBoxVRDP)
- Guest is using all default settings

Edit: Forgot to mention, as for anti-virus, firewalls, protection software, and debugging programs, I only have:
- Windows Firewall
- Microsoft Security Essentials (with real-time protection turned off)

[loukingjr]

See: viewtopic.php?f=6&t=64777

[sanitykey]

Thanks loukingjr, I wasn't sure if I should put this there as I'm using 4.3.21, but I see at the end of the thread people are also using this version so in retrospect I probably should have

[loukingjr]

no problem.