@Lesil
By your post edit saying 'solved', i guess you've already worked out that when cure firmware is loaded the device CANNOT fully boot and it's quite intentional that it stalls on the logo screen before it can load any essential files like maps, voices, POIs, etc.. The only purpose of cure fw in fact, is to re-enable Mass Storage Mode (BTW, GarminExpress only sees devices which have Mass Storage or MTP modes available).

After you've removed any offending file/s or formatted, the ORIGINAL firmware must be loaded as an RGN file in preboot mode to allow the device to boot fully. When it does boot, it automatically re-creates the XML file as it does so on every boot cycle. If you formatted the 3760 you will need to load another basemap manually because GE won't offer a replacement: [Only registered and activated users can see links. ]