Suddenly receiving a bunch of warnings - no code changed.

There has been no change in code for at least a month.

First received this:

[30-Mar-2014 22:17:07 Europe/Helsinki] PHP Warning:  Illegal string offset 'title' in /home/fh2fuvvy/public_html/includes/modules/pages/checkout_shipping/header_php.php on line 88

then this:

[31-Mar-2014 18:00:18 Europe/Helsinki] PHP Warning:  Illegal string offset 'cost' in /home/fh2fuvvy/public_html/includes/classes/order.php on line 355
[31-Mar-2014 18:00:18 Europe/Helsinki] PHP Warning:  Illegal string offset 'id' in /home/fh2fuvvy/public_html/includes/classes/shipping.php on line 32
[31-Mar-2014 18:00:18 Europe/Helsinki] PHP Warning:  Illegal string offset 'id' in /home/fh2fuvvy/public_html/includes/classes/shipping.php on line 32
[31-Mar-2014 18:00:18 Europe/Helsinki] PHP Warning:  Illegal string offset 'id' in /home/fh2fuvvy/public_html/includes/modules/order_total/ot_shipping.php on line 41
[31-Mar-2014 18:00:18 Europe/Helsinki] PHP Warning:  Illegal string offset 'id' in /home/fh2fuvvy/public_html/includes/modules/order_total/ot_shipping.php on line 41

Did your hoster by any chance upgrade to php 5.4?