TT6 Map manager not seeing New England

[smis]

Hi,
I've been running TomTom 6 on my unlocked icn520 for some time using a copy of UK IE and WE maps.

I'm off to New England so I thought I'll install a map for the area.

I've obtained a map for the area I need and the format looks the same as the UK one.

When I load it onto my SD card next to the directory of the UK map the ICN520 dosn't see it.

I've done the same for a Gaum (sp) map with no problems.

I'm looking via the navigator map manager page located in the preference directory.

Any ideas ?

Many Thanks