A while back, I bought the item Glacier Ice to change my faction, but when I went to Account -> Change Faction Allegiance, my current faction is listed as blank despite being part of the Neutrals. Thus, when I try to change my faction by selecting any faction different than mine, I get "Invalid form data" instead.

Here's an image:

When did you try to change allegiance? If it was today then you can't because of the FMC.

Ohh -- I'm not sure if I ever tried it when it isn't FMC season. I'll try it again when FMC isn't running -- thank you!