Ok, so I use the paypal plugin with firefox, which is really nice because you can generate single use credit-cards on the fly. However, recently it's been acting strange.

Normally, when you use the plugin, a drop-down window open in firefox. However, at some point (I'm not sure exactly when it happened, because I thought it wasn't working for a while) the drop-down window started appearing in thunderbird.

As in, I click on the plugin button in firefox, and the plugin window immediately opens in Thunderbird.
If Thunderbird is closed, the plugin does not open at all.

I can use it normally this way (everything works except the receipt-saving function). but the whole affair seems a little odd to me.

Is there any reason that could cause things to be redirected from one mozilla-application-window to another mozilla-application-window?

Everything is up to date:
Firefox 3.6.3
Thunderbird 3.0.5 Paypal Plugin 2.2.26.0