Hi DBMaster ...
You have a good change you are using chello as a ISP ... because chello has a very persistent cache ... they like to save on real bandwith ... (but some other providers do it too ...)
Since you are still in the 5 series you will ask for a HTML page and since this page was already requested it still resides in the ISP's cache (not in your browser cache, because the meta tags are correct in a standard UBB, unless you altered them of course) ...
Two solutions are at hand ...
Upgrade to 6 since this will solve the cache issue by your provider since you call a cgi instead of html page and this is always build dynamicly ...
Second, but not that easy ... send a very very friendly and polite mail to the support desk of your ISP and ask them to add your URL to the ignore list of their caching system ... (you have a good chance they won't)
Greetz
Knuff