Saving settings page generate 404 error or blank page.

If you notice Booking > Settings General page is not saving, Suhosin (a security module in PHP) may be preventing the POST data from being saved. This issue can also be caused by servers with version PHP 5.3.9+ and servers running mod_security.

If enabled, Suhosin may need to be configured to increase its data submission limits. Changing Suhsoin settings differ from host to host so it’s usually better to consult with the provider than attempt it yourself, however some hosts allow you to change settings via php.ini, suhosin.ini, or .htaccess.
Commonly, the following vars will need changing:

General PHP section

memory_limit = 256M
max_execution_time = 120
post_max_size = 8M
upload_max_filesize = 8M
max_input_vars = 20480
post_max_size = 64M

Suhosin section

suhosin.post.max_array_index_length = 1024
suhosin.post.max_totalname_length = 65535
suhosin.post.max_vars = 2048
suhosin.post.max_value_length = 1000000
suhosin.post.max_name_length = 256
suhosin.post.max_array_depth = 1000
suhosin.request.max_array_index_length = 1024
suhosin.request.max_totalname_length = 65535
suhosin.request.max_vars = 2048
suhosin.request.max_value_length = 1000000
suhosin.request.max_varname_length = 256
suhosin.request.max_array_depth = 1000

After saving you will need to restart the server for the changes to take effect. See http://www.hardened-php.net/suhosin/configuration.html for more information on Suhosin settings.

In shared hosting environments it may not be possible to edit php.ini, in which case you may be able to set the suhosin settings via .htaccess
It is still recommended however to consult your hosting providers documentation, or raise a ticket with them for assistance.