Browser Won't Insert Text

Mac G4 1.8Ghz running 10.3. Occasionally, various webpages will not
accept inserted text in Safari, Mozilla, and Firefox. Rebooting,
re-installing,
repairing permissions, doesn't work.

It's particularly annoying using Pair.com mail, which relies on the
browser
window.

Any ideas what could cause this? Strange parameter corruptions? Option
not set right? PHP errors?  Any ideas????


Mark