Language vector updates to production site not visible

[ploughguy]

Ho, CubeCarters! I have a truly strange problem which I am hoping some CC-proctologist or WebServer Master might be able to help me with. Or perhaps a complete novice can point out my dumb mistake...

I have created a custom language vector file en/custom.inc.php which holds texts for my personal additions. The object clearly being to keep my stuff separate from the standard product in the infantile hope that one day I will have the courage to update. I have integrated the language vector into the standard language maintenance facility in the Admin page and it has been working fine for 6 months.

I have added a new and useful feature which allows a customer to get a postage quote on the cart page. Above the shipping options drop-list, there is a caption "Quote postage to", two entry fields (postcode and droplist for activated countries) and a "Quote!" link that updates the price. (The hope is to capture those who get to this point, realise they cannot get a final price without putting in personal details, get all indignant and decide to bail. My old lady is one of these...)

I coded it up, sent it to my test site which is on a local linux VM, and it worked perfectly. I shipped it to the hosted production system and it bombs because the language vector is providing the default country and postcode (easiest place to put it.)

First thing I did was clear the caches but no change. I put some debug in to print the language vector strings and they are blank. In the Admin page, I can see the strings have values, and when I overwrite them and update, suddenly the page works.

So the update of the files was correct, the code is working correctly, I can see that the texts are in place in Admin, and if I update them in Admin, (which creates a copy in the database which overrides the file) then it all works, which means that the language caching is working correctly internally. However, before the update, the web server was not seeing the new version of the file. There were a bunch of PHP files which were updated, and their changes came through as expected.

Both web servers are apache, both are running on Linux. The test system has had minimum configuration done, and I have no idea how the hosted server is configured.

I would like to eliminate this behaviour because every time I upload a new feature with new strings I have conniptions because I think I have broken it until I remember about the web server and the text files. (Last time, the problem was not fixed until the hosting folks rebooted the server. Now I have worked out the update-the-language-vector trick, I can goose it myself, - - I think.)

Any ideas?

R