not recognizing pw on login - ubuntu 32-bit on W7 host

[rb7]

I installed 5.0.4 on my Windows 7 32-bit machine.
Then, I installed ubuntu 32-bit version as a guest OS.
All worked fine for a couple of days. But suddenly, my password would not be recognized and I continue to be in login screen.
It throws no error message (would simply get me back to the login screen that asks for my password).
As a check, I would re-install Virtual Box and Ubuntu from scratch. Similar problem exists (after working fine for a few days).

I appreciate any inputs.

Thank you very much for your help!

[socratis]

Why do you think that it is a problem with VirtualBox? Do you have multiple keyboard layouts that may confuse your guest? Also, I don't understand the following statement:

Similar problem exists (after working fine for a few days).

Can you elaborate on this? What does "similar" mean? And what happens between working and not working? Read the following article and provide the logs requested in your reply: Minimum information needed for assistance.