I have this ConcurrentMap
ConcurrentMap<String, Byte> companyLogo = new MapMaker()
companyLogo.put("cpr48124", ArrayUtils.toObject(resize (request, ((Byte)request.getSession().getAttribute(COMPANY_LOGO_KEY+ imageId)))));
I'm not familiar with
MapMaker is, but I'd guess that
weakKeys might be your problem.
It is likely that the 'weakness' of your new entry is making it unavailable since there are no other references to it.