Custom text input field ampersand (&) truncates entry

[JeremyD]

Just encountered a problem where if a customer enters an ampersand into the custom text input field, the text is truncated at the ampersand when the product is added to the cart.

e.g. David & Julie gets truncated to just David

As far as I can see all other normal characters and punctuation are stored correctly, just & and it doesn't seem to affect any other functionality.

Anyone got any ideas as to what's causing that? I'm assuming some form of character set issue, or other filtering problem, but no idea as to where to start looking at the moment.