Error loading offline maps

Hi,
I previously installed the application and had no problem using it. I imported offline maps in the omc2 format and was able to use them. At some point I noticed I'm unable to use the offline maps anymore. I've tried using older versions of the application but they demonstrate the same behaviour. I select the maps folder, The message "Loading maps:.." appears but the application displays only the "Waiting" icons (circles or a circle of two arrows, depending on the software version) instead of the maps. I'm running 4.0.3 on a Galaxy S2, at the moment. All the calibration files are present in the maps directory structure and I can't figure out a reason for the maps not being displayed. Using the OI file explorer to browse the map folders I am able to see the files and view them with the gallery however, browsing with the regular explorer shows the files but I'm unable to view them, "No Application can perform this operation".
Has anyone encountered similar behaviour? I'm probably missing out on something basic....
Thanks,
dp63

Update - I still don't know why the maps in the omc2 format failed to load but I regenerated the maps using MOBAC and changed the settings to generate sqlite format maps. Now everything is working fine again.