The same problem (though concerning BC Manager) was reported here.
As I explained in that topic, the direct cause of the error message is that the application's stp-file (for FCB1010 Manager: "fcbman.stp") or mru-file ("fcbman.mru") doesn't start with the correct header line ("[FCB1010 Manager]").

However, I still don't know the underlying cause of the problem.
So it would help greatly if you could tell me what these configuration files currently look like on your system.
E.g. is one of these files empty, or truncated, or does it contain garbage, or is it locked by the operating system?

You may be able to determine what's wrong exactly as follows:

Open a terminal window, e.g. via Applications -> Utilities -> "Terminal.app".
In this window, enter the following commands:

First, go to FCB1010 Manager's configuration folder:
cd ~/.config/mountain_utilities/fcbman

Then get a list of the files in that folder:
ls -l
On my system this gave me:
-rw-r--r--  1 mark  staff   207 Nov  9 14:07 fcbman.ini
-rw-r--r--  1 mark  staff   523 Nov  9 14:07 fcbman.mru
-rw-r--r--  1 mark  staff  2626 Nov  9 14:07 fcbman.stp
So are any of these files missing on your system?
And look at the fifth column, containing the file sizes: these should be roughly the same as on my system.
(A size of 0 would be bad, and so would be a very small or very big value.)

A simple way to see the actual content of each file is this:

more fcbman.ini
For me this returned:
[FCB1010 Manager]
Version=2.2.0
SetupFile=/Users/mark/.config/mountain_utilities/fcbman/fcbman.stp
AutoSaveSetup=1
UpdateAutoCheck=0
UpdateFrequency=30
UpdateMinDevelopmentStage=0
UpdateLastCheck=-1

more fcbman.stp
For me this returned:
[FCB1010 Manager]
Version=2.2.0
OpenDir=/Users/mark
SaveDir=/Users/mark
(etc.)

more fcbman.mru
For me this returned:
FCB1010 Manager]
Version=2.2.0
SetupFile1=/Users/mark/.config/mountain_utilities/fcbman/fcbman.stp
SetupFile2=
(etc.)

Note: the ~/.config/mountain_utilities/fcbman folder is hidden, so it doesn't show up in Finder, unless you allow Finder to show hidden folders.
So if you want to look at these files in a text editor (TextEdit.app or whatever), it may be easier to copy them to your desktop:
cp fcbman.* ~/desktop
Then you can simply open these copies in your favorite text editor from Finder.

Good luck!
   Mark.