PHP Timezone database is corrupt error

I have a wordpress website which suddenly stopped working today. When I look at the logs I see and error:

[error] [client 50.78.108.177] PHP Fatal error: strtotime(): Timezone database is corrupt - this should never happen!

After reading up on google one person said that they discovered a permissions problem in /usr/share/zoneinfo. I tried changing the permissions to 777, 775, 770 and I still keep on getting the same error. I am running php PHP 5.3.2 on Ubuntu 10.04.3 LTS. Any suggestions or recommendations would be helpful.If all else fails I'm going to try downgrading to an earlier version of php but I wanted to try other things before doing that.

thanks, Timnit

Update
just in case it helps: the error points to strtotime in the function below

function mysql2date( $dateformatstring, $mysqlstring, $translate = true ) {
    $m = $mysqlstring;
    if ( empty( $m ) )
            return false;

    if ( 'G' == $dateformatstring )
            return strtotime( $m . ' +0000' );

    $i = strtotime( $m );

    if ( 'U' == $dateformatstring )
            return $i;

    if ( $translate )
            return date_i18n( $dateformatstring, $i );
    else
            return date( $dateformatstring, $i );
}

Update#2:
for now I have fixed the problem by simply having the function above return false; without performing anything. However I still haven't figured out the root cause of the problem.

update#3:

var_dump($dateformatstring)

string(5) "d.m.y" string(1) "m" string(5) "d.m.y" string(1) "m" string(5) "d.m.y" string(1) "m"

var_dump($mysqlstring)

string(19) "2011-10-20 05:35:01" string(19) "2011-10-20 05:35:01" string(19) "2011-10-20 05:25:22" string(19)