[Typo3] upgrading to 3.7 problems

[Cyro Pintos]

Hi,
Trying to upgrade to Typo3 3.7, after replacing the folders i get the 
following line in the Administration Login in Quickstart:

 Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result 
resource in C:\apache\htdocs\quickstart\typo3\t3lib\class.t3lib_db.php on 
line 723

It doesn´t allow me to login with the usual password.
Any help would be appreciated.
Thanks in advance.

Cyro