It appears that older version of quickcart (version 3) does not work with the newest version of php.
Unfortanately i cannot install older versions of php, and i will not migrate to version quickcart 4 as this will required redoing all the templates/css etc.
I have tried these solutions, without success. http://opensolution.org/faq-i-cant-add-new-or-save-already-existing-pages-products,en,154,215.html?iPopup=
If anyone is interested on working on a permanent fix that will make quickcart 3 work on the latest version of php 5.4, please email me your fee estimates at dcistudios @ gmail.com
Older version of Quick.Cart works even with php 5.5 ! So I think it may be caused by some server configuration or error in your script. Try to turn on error reporting or ask your server admin are there some errors in logs. Also write what you mean by writing "does not work" it it only some functions or it is not working at all?
If when saving page or product data you get no error message, but a message says the data has been saved properly even though they are not, the most probable cause is the size limit of the form that can be sent by the server. This problem occurs when the limit on the form sent is low or you have a 1000+ files on your server. The problem with saving data and large number of files on the server is solved in the latest version.
This is not strict PHP limit but suhosin patch: http://opensolution.org/faq-i-cant-add-new-or-save-already-existing-pages-products,en,154,215.html?sOld=true
Or there may be also suhosin patch on your server and limit in it. It is very popular and it you have a lot of files on your server it may be problem. It was solved another way in newer version so script creates less fields. More in link I sent before.