Strange issue with entering passphrase (security chip)

[ithacam5]

On my new X60s, I opted to use the security chip and pass phrase
for login. This all worked fine initially. However, I noticed that after
placing the laptop on standby it will occasionally refuse the pass
phrase claiming it is invalid.

I've checked caps lock, I know it was correct. I then tried answering
my security questions and it claimed my answers were incorrect. I
thought perhaps after coming out of standby, the security chip did
not initialize properly so I hibernated the notebook.
When I woke it back up, it asked for the pass phrase, and I
entered it again and all worked fine.

I've noticed that there seems to be an issue with this since it has
happened occasionally since then. Is this a known issue ? Perhaps
I'll go back to using the windows password....