V 1.3.6, no recent changes.
I am getting these error randomly in the store and admin:

ADMIN gets this:
Fatal error: Call to undefined function: preg_match() in /home/qualityw/public_html/store/admin/includes/application_top.php on line 109

STORE gets this:
Fatal error: Call to undefined function: preg_match() in /home/qualityw/public_html/store/admin/includes/application_top.php on line 80

www.qualitywindowscreen.com

Anyone know what is happening?
Dan