Yes, that would be my first guess as well, though it is difficult to tell
without seeing them.
120 film isnt the best light sealed thing, nowhere near as good as 35mm,
so if the roll has come slightly loose, it does allow a small amount of
light to creep round the edges when loading.
At least you didnt do what I did a few months ago - I loaded the film the
wrong way round, and only realised when I took the film out.Luckily I was
taking pics of an old cathedral, and still had time to retake the ones I'd
already 'lost'.
Alan.

Just re-checked the fix time on agfa's site. 6-8 mins not 30secs for
1:7 diluation, I looked at details for the wrong fixer! oops. Doesn't
explain the edges though, but could have been while loading the film
as suggested by you guys.

I'll shoot another roll tomorrow and try again...
--
Mark

HP-4 is a conventional emulsion. It should fix out in twice
the clearing time. Some tabular grain films may need more to
fix out completely but I've not seen any real substantiation
of this. In any case more than three times the clearing time
is unecessary.
   For film strength rapid fixer the clearing time for
conventional emulsions should be on the order of one to
three minutes and total fixing time on the order of double
that. I completely agree with maing a clearing test but
advise soaking the test film in water for a couple of
minutes. The reason is that wet film fixes at a different
rate than dry film. Early researchers into the optimum
concentration of thiosulfate ran into this effect. The found
a value of thiosulfate where the fixing time appeared to be
a minimum. Later research showed that this was an effect of
fixing dry film. When wet there was no optimum and fixing
continued to become shorter with increasing concentration.
  Also, refix the film, it should clear. Also, treat it in
Kodak Hypo Clearing Agent, as directed, after the refixing.
This may help to remove some fixing reaction products which
are not converted to a soluble form if refixing is not
within about 48 hours of the original fixing process. Wash
as directed on the wash aid package.
  Fixing time varies with the emulsion for any type of
fixer. Very slow chloride emulsions, as found in contact
paper like Kodak Azo, fix out very rapidly. Fast film
emulsions, which have a lot of silver iodide in them, fix
out very slowly even in rapid fixer. It may be the high
iodide content of T-Max and Delta films which makes them
slow to fix out.