I'm guessing a fusebox configuration issue of some sort. The only time I have seen behavior like you're describing is when the fusebox mode was set to "development-full-load" instead of "production". Fusebox is not thread safe in development-full-load mode and it can cause some strange results. Also make sure you have a parsed folder under your site root with read-write access - but I think this would throw a different exception.
Thank you Steve, would this be the one in fusebox.xml.cfm ?
<parameter name="fuseactionVariable" value="page" />
<parameter name="defaultFuseaction" value="home.index" />
<parameter name="precedenceFormOrUrl" value="form" />
<parameter name="password" value="spharm_app1" />
<parameter name="execute" value="true" />
<parameter name="reparse" value="true" />
<parameter name="parseWithComments" value="false" />
<parameter name="mode" value="development" />
<parameter name="scriptlanguage" value="cfmx" />
<parameter name="scriptFileDelimiter" value="cfm" />
<parameter name="maskedFileDelimiters" value="htm,cfm,cfml,php,php4,asp,aspx" />
The site has been running for about 10 years and we noticed this behaviour since CF9 was upgraded to CF10, I have also been told that we should upgrade fusebox itself from 4 to 5 ?
Could that be also to do with it ?
Yes we do have a parsed folder.
Yes, the line you highlighted should not (cannot in my experience) be set development on a production server. Try canging that setting to "production" and restart your site - or reload it via the fb reload parameter and password.