Impossible to verify the digital signature

[Khorden]

Hello everyone, I've installed Virtualbox 4.3.14 on Windows 7 host with Ubuntu 64 guest.

I'm writing my first post because I'm facing a periodic error.

The first time I installed Virtualbox everything worked fine, I used my vm without any problem and at the end I turned off the pc. The next day I tried to start virtualbox but an error message came out:

C:\Program Files\Oracle\VirtualBox\VirtualBox.exe

Windows: impossible to verify the digital signature. After an hardware or software modification, it is possible that it's been installed a damaged file, with an uncorrect signature or an unknown malware.

Afterwards I removed and reinstalled Virtualbox, and everything worked again... but only till the shut down: on the next reboot I faced the same error.
Every next reboot I'm unable to start Virtualbox because this error window pops up and the only solution I've found is to re-install Virtualbox every time.

Any idea to resolve? Thank you in advance and sorry about errors in english and/or in reporting this issue.

[Khorden]

A little update: it seems that the error doesn't occur when I shut down and reboot in the same day...maybe it's connected to the passing of days? Something about the internal system clock?