Forum won't accept new registrations

[mctaz]

One of my forums (1.1.19) seemingly won't accept new registrations, it goes through the registration process then at the end when you hit Submit, it says "An error has occurred"..
It has been working flawlessly for years, and I've made no changes, any ideas what could be wrong?
Thanks

[Kindred]

Ask your host if they changed anything

[Illori]

what mods do you have installed?