Abalabo:
The memory_limit I have set to 384M in my little php.ini file and that is what I see in the full php_info report that you referenced (System -> Settings -> System and then PHP info button top left). From what I've seen I think this is way over the top.
Barasa:
I have contacted my hosting provider and I have given above the information that they provided. They seemed unable to help further. It almost looks like a bug in PHP, but this has only recently started happening. What I said was:
Looking at the last 30 days, there have been periods when (14-15, 22-25 Nov) when the virtual memory limit has been reached, but I have only experienced these error messages 'Internal Server Error' in the last day or so.
This makes me think the answer lies in the code of Abantecart which is way beyond my understanding at the moment.
Another thing I tried was to 'switch off' the Foxy template which I bought and installed some time ago and I think recently has been automatically updated. This made no difference.
Could this possibly be the problem?
The only substantial change I made in the short time before this started happening was to change the code of the 'Royal Mail' shipping extension (extensions/default_royal_mail/storefront/model/extension/default_royal_mail.php) and to add a new shipping extension 'Yodel' which was modelled on the 'Royal Mail' one. Now I added that extension simply by adding the new folder 'default_yodel' with all the necessary files (which I had previously debugged in my offline copy of AbanteCart on my local machine) to the extensions folder. I had logged out from the control panel before doing this. My understanding was when the extensions page was brought up, Abantecart would find the new extension and add it to its internal data (this extension makes no SQL changes) and everything would be fine, and it was. The extension worked (apart from some language 'translations') and the desired extra shipping options appeared in the checkout. Soon afterwards I started getting these Internal Server Errors.
So one of these could be the suspicious culprit, right?
Ok, so I uninstalled both these extensions and deleted them using the buttons on the extensions page. I then physically moved the default_royal_mail and default_yodel folders to be under the tmp folder, out of the way. AbanteCart shouldn't see them there. So these extensions cannot in any way be responsible for these errors. But I still get them. Is it possible that some residual entries in the database might remain which could be throwing a spanner in the works? (Well I found some in the dataset tables, but these seem to be recording the installing and uninstalling of the extensions. It's hard to think these could be responsible.)
Is it possible that the database has become corrupted?
Do I have to do a complete reinstall?
Any other suggestions? Would my sending you a verbose debug log help?
Thanks for your attention so far.