I don't know how Barry Andrews solve his problem, but I can share the knowledge how I solve mine :-)
Inside my DLL I used WinAPI function available only in Windows Vista (and later). However I was running the application under Windows XP....
The tool that helps me solving my problem -
http://dependencywalker.com
Check your DLL with it, and you must NOT have any errors like "At least one module has an unresolved import due to a missing export function in an implicitly dependent module".
It may be OK if you have problems with delay-load modules (missing delay-load dependencies are not a problem as long as the calling DLL is prepared to handle the missing module - see the dependencywalker FAQ)
Cheers,
thexman