I've managed to solve this.
I recently installed GIMP (the open source image editing suite) and this seems to have caused the issue. GIMP needs the GTK+ Runtime Environment, part of this installs a copy of iconv.dll and renames any other versions of that .dll that reside on the PC. Unfortunately, iconv.dll exists in \Bladelogic\OM\bin and this had been renamed to iconv.dll.OFF. Uninstalling GTK+ and renaming the original copy of the dll has resolved the issue.
Just thought I ought to share.