Once a bankruptcy is filed, creditors cannot take actions to perfect liens against property for debts that arose prior to the case filing. If the debt arose post-petition, then the lien could be valid. You will need to have your attorney review all of the paperwork to determine whether or not the lien is valid.
As to maintenance fees in paritcular, post-petition debt you will be liable for; however, pre-petition debt you are not. Therefore I recommend you request an itemization of unpaid maintenance fees so you can ensure that the fees being sought are correct. Attempt to do a settlement on the outstanding fees owed post-petition. You may also want to complete a short sale or a deed in lieu of foreclosure to get the property out of your name.
The above information is not intended as legal advice. If you have any legal questions consult with an attorney of your own choosing.