->Cookies, I think.
I have the feeling that the reporter might have been confused by the symptoms that he reported. Specifically, I don't think that the numeric entry had anything to do with it -- adding any entry would have had the same effect. Turns out there is a hard-coded limit on the size of a buffer used in nsCookie.cpp. See bug 62057. I believe that this is what you were running into. I'm currently working on a fix for that bug. *** This bug has been marked as a duplicate of 62057 ***
It definitely looked similar at the time, but seemed to behave differently. My original test was to remove all of the entries that were numeric, and the image manager started working. When I added a numeric entry, it stopped. If I added a text entry, the image manager still worked. As long as the root cause has been discovered! 8^)
I tried it with a very small cookperm.txt file and added a numeric entry. It did not present any problem. I suspect that what was happening in your case was that the numeric entry and the non-numeric entry were of different sizes. The problem is not on the number of total entries but on the number of total characters in all the entries. So adding the non-numeric entry in your case might not have put you over the limit but adding the (probably longer) numberic entry did.