I can't live without TextExpander. But apparentely Firefox and Chrome are not playing nicely with it. TextExpander suddenly stopped working for. I don't use these browsers very often, most for browser testing. Anyway, here is an explanation from TextExpander support:
Most likely, you're being affected by the bug in Firefox and Chrome where they enable secure input but don't disable it. This bug is particularly infuriating because it doesn't seem clear to the end user what causes it. However, it does have a cause, a workaround, and it does seem to be getting some traction from the Mozilla folks. Switching product probably won't help, as the other text expansion applications observe input in the same way as TextExpander and thus are subject to deprivation by secure event input being left enabled. When these browsers display a password field, they turn on secure event input so that no one, including TextExpander, can peek at your passwords. Problem is, if you use the Return key to submit a form from within its secure field, they won't turn secure event input off. This appears to be a bug they've inherited from some Firefox code they use. The workaround is to use the submit button rather than using Return in the password field. 1Password is similarly affected by this bug. The workaround there is to turn off auto-submit and just use auto-fill then press the button to submit.
This is referenced on Mozilla's bug tracker.