None of these suggestions work. Some more detail: on a command line as root, if I enter the directory the file is in, 'ls' without any parameters produces the following output:
/bin/ls: powErpmc250.h: File or directory not found (actually that is in German)
So it does see the file, as it gives me its correct name, but cannot handle it, paradoxically giving me its name while stating it can't find the file.
In mc the filename is the same but with a ? in front, and it is red - the colour mc on my system uses to mark erroneous things such as symlinks missing their target. Mc lists the file as zero length and with a date of Jan 1st 1970.
I can even touch powErpmc250.h in the same directory, after which I have two files of the same name in there, with no question mark. The question mark reappears when I delete one, I can't delete both at once, nor the directory they're in. If I copy another file into the directory and change its name to the same as the offending file, both are listed with identical properties, but only one can be deleted, one always remains and reverts to zero length etc.