I am experiencing a strange glitch with low value products. If the difference between the price and the special price is below £35, the special price is showing as £0. If I change the price to more than £35 difference everything resorts to normal. I've uploaded via magmi and via the magento product backend but the issue occurs either way, which makes me think something has gone awry with a config setting somewhere. Anyone ever had any experience of this or have any idea what might be causing it?
Not something I've ever experienced. Best check all your pricing/promotional rules. Perhaps you have an old rule that has been removed, but the reapply of promotional rules needs to be run to resolve.
I have in some cases seen hosting environments so improperly set up that InnoDB was disabled on the MySQL server, leaving every table set to MyISAM - and thus promotional rules were catastrophically broken because the foreign key relationships were destroyed. Check your DB tables are in fact innodb (the majority should be)