HELP - URGENT - Site gone white

-- url of the page with the problem -- : www.raysicecream.co.uk
-- HikaShop version -- : 2.2.2
-- Joomla version -- : 1.5
-- PHP version -- :5.2
-- Browser(s) name and version -- : firefox

Hi Installed version 2.2.2 as I thought would be compatible with joomla 1.5. All working fine until today. Site went white. I can log into the admin panel but front end completely white. How do I fix this?
Thank you

-- Error-message(debug-mod must be tuned on) -- :raysicecream.co.uk [Wed Nov 13 16:28:27 2013] [error] [client 94.195.48.85:53911] AH01215: PHP Fatal error: Call to undefined function hikashop_get() in /home/sites/raysicecream.co.uk/public_html/plugins/system/hikashopproductinsert.php on line 28
raysicecream.co.uk [Wed Nov 13 16:32:54 2013] [error] [client 94.195.48.85:54093] AH01215: PHP Fatal error: Call to undefined function hikashop_get() in /home/sites/raysicecream.co.uk/public_html/plugins/system/hikashopproductinsert.php on line 28
raysicecream.co.uk [Wed Nov 13 16:32:57 2013] [error] [client 94.195.48.85:54058] AH01215: PHP Fatal error: Call to undefined function hikashop_get() in /home/sites/raysicecream.co.uk/public_html/plugins/system/hikashopproductinsert.php on line 28
raysicecream.co.uk [Wed Nov 13 16:37:28 2013] [error] [client 94.195.48.85:54255] AH01215: PHP Fatal error: Call to undefined function hikashop_get() in /home/sites/raysicecream.co.uk/public_html/plugins/system/hikashopproductinsert.php on line 28

Hi,
The shop was installed 3 weeks ago, are they up to date?? I've attached a screen shot of my plug ins filtered. None exactly as you mentioned...is it in this screen shot?
Thank you

ps if they are not up to date how to I update them?

Hi
I just noticed I was looking at the update version. You're right. I downloaded 2.2.2 but its a .tar file (not .zip) when I try to install it my screen just goes white. Am I using the wrong file and should this fix it?
Thankyou

Hi This is the error - seems to be the memory? Do you knwo how to go about increasing the memory...do I need to talk to my hosting provider?
raysicecream.co.uk [Thu Nov 14 09:34:18 2013] [error] [client 86.129.251.76:49496] AH01215: PHP Fatal error: Allowed memory size of 25165824 bytes exhausted (tried to allocate 13667656 bytes) in /home/sites/raysicecream.co.uk/public_html/libraries/joomla/filesystem/archive/gzip.php on line 77
raysicecream.co.uk [Thu Nov 14 09:34:19 2013] [error] [client 81.139.66.45:64111] AH01215: PHP Fatal error: Call to undefined function hikashop_get() in /home/sites/raysicecream.co.uk/public_html/plugins/system/hikashopproductinsert.php on line 28

Hi,

You can try to edit the .htaccess file at the root folder of your website and add/edit the line:

php_value memory_limit 64M

Xavier, I have a website back! on your suggestion. I haven't tested the shop yet but I am so relieved my site is no longer pure white!
Thank you

Hi Jerome,
rays Ice cream, before I upgraded, the check out worked. I'm sure I'm missing something simple but now there is no way of 'checking out' or actually buying anything. You can click on the cake and see the description, but there's nowhere to go from there. I didn't change anything, just upgraded. Please help!
Thank you
Julia

Hi,
Yes sorry, My site owner turned it off as she didn't want anyone trying to buy anything. When you click through to the product there is no add to basket button. I've attached a screen shot. I have turned the shop off again, just let me know if you need it on and I'll let her know it's been turned back on.
Thank you

HI,
I've been asked to do the following...
"I thought there was a box for comments on the Paypal checkout and I've put in the title for our shop that people need to leave us a message there with when they want to collect their cake. But I can see no such box in Paypal". Can we somehow get this option added to the checkout?
Is there somewhere on check out people can add comments to their order? Thank you