virtualbox.org

VirtualBox 4.3.18 r96516

Since I installed this version I get the following error when I run any of my guest machines:

Failed to open a session for the virtual machine LinuxMint.
Unable to load R3 module C:\Program Files\Oracle\VirtualBox/VBoxDD.DLL (VBoxDD): GetLastError=1790 (VERR_UNRESOLVED_ERROR).
Result Code: E_FAIL (0x80004005)
Component: Console
Interface: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

I noticed the forward slash (/) in the path name for the module. Could that be the culprit? If so, how do I fix?

No, the slash is not important. You should try reverting to 4.3.12, and keep an eye on the "security" discussion stickied at the top of this forum.