To just start firefox with default settings, rename (not delete to enable error analyis) the directory hdonk_firefox_001 in the pandora/appdata directory of the card containing the firefox PND. After that firefox should start up and create a new hdonk_firefox_001 directory with default settings.
To analzyse your problem, take a look at the file .mozilla/firefox/profiles.ini in your old (now renamed if you did the above steps) appdata directory. (Note that the .mozilla directory may be hidden in the file manager; you can enable display of hidden files somewhere in the preferences; files starting with a dot are hidden files in unix.) The error message indicates that the entry in the line Path=points to a nonexisting directory. If you can locate the correct directory you can either move it to where profile.ini is pointing to or change profile.ini to point to the correct location.
In the worst case you did delete your profile by accident e.g. while copying it to somewhere else and not copying the hidden .mozilla directory. (It can be confusing that the firefox PND creates both a mozilla and a .mozilla directory; the former contains temporary data while the latter hidden one contains the actual configuration; these are separate because on windows these are located in different parts of the user's profile, to not synchronize the temporary data across the network).