About a year ago I received a gift of a Memory Map branded Adventurer 2800 complete with OS 1:50k map pre-installed that I have used frequently. Several weeks ago the map wouldn't open and on linking to my PC saw that the map had a file size of 0kb as opposed to the same map on the PC being 3,118.805kb. I managed to copy the map from the PC to the Adventurer but when I try to open it on the GPS get the error message: "Could not open file \SDMM Card\Maps\OS50\OS50_GB.QCT". Clicking OK repeats the file detail but preceded by "Failed to open file".
I have sent three queries to support through the Memory Map support site about this but haven't had any reply yet. I also posted the query on the registration & licensing section of this forum where I have received some advice and possible solutions, but it looks as though I still require assistance from Support. Advice given from that part of the forum was
The original GB map file on the Adventurer (SD card) would have been in .QC3 format (with a small .QCT "sidecar" file) but on your PC the map is probably in a single .QCT format file (~3GB). The Adventurer can read .QC3 files up to the filing system limit (4GB) but .QCT files only up to about 400MB. If you have somehow "lost" the original .QC3 file on the Adventurer, you will either have to try to get it replaced by technical support or "cut" the PC's .QCT map file into sections of less than 400MB as described on page 7 of the user manual posted above.
A further complication is that trying to open the map on the GPS seems to have caused the creation of a file on the GPS with what looks like Wingdings font and a file size of 86.9Mb, although when I link the Adventurer 2800 to my PC and check the Maps folder for the Adventurer it shows that it is a Memory-Map QuickChart file 'os50_ g' file of size 88.960kb.
How do I get a working OS 1:50k map back again on my Adventurer please?
One other thing, I am unable to link the Memory Map software on my PC to the Adventurer even though in GPS setup in the Memory Map software I choose USB connection and manufacturer as Garmin; that simply results in the software error message, 'GPS: Garmin not connected'. Hence, the only way to transfer tracks/routes between the PC and the Adenturer is to copy the track from the relevant folder on one and then paste it to the relevant folder on the other. It it indeed impossible to connect the Adventurer 2800 to my PC to import and export tracks and routes as Memory Map software communicates through Windows Explorer (W7 in my case) and not through the GPS or Mobile Device menu options?

This is the best advice. The best way to tell if the map is an older (non-encrypted) map is the QCT file. If the QCT file is roughly 18kb in size, it should have an associated QC3 file of much larger size. The older maps (only QCT) would be contained in one file and would be larger than 18kb. I would delete the 89Mb file and try to copy again. I would certainly contact UK tech support (support@memory-map.co.uk) about possibly reloading the SD card.

I have e-mailed support and hope they will respond with the solution.
Thanks