Firefox and onscroll failing from greasemonkey

I've noticed that a greasemonkey script I wrote a while back is no longer working, maybe due to me using Firefox 4 now (although I don't have an earlier version of Firefox on hand with which I could verify this theory).

It does the following:

myelm.addEventListener('scroll', fonscroll, false);

This used to work, but now it seems to fail silently. Moreover, if I try the following instead:

myelm.onscroll = fonscroll;

I get the following error:

[Exception... "Component is not available"  nsresult: "0x80040111 (NS_ERROR_NOT_AVAILABLE)"  location: "JS fr开发者_如何学JAVAame :: jar:file:///~/AppData/Roaming/Mozilla/Firefox/Profiles/wo832x2w.default/extensions/%7Be4a8a97b-f2ed-450b-b12d-ee082ba24781%7D.xpi!/components/greasemonkey.js

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what is the element type of myelm? I tried to add a scroll event listener to an iframe

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This has been resolved. It turns out that Firefox no longer likes to let me use CSS to scroll a tbody independently of its thead. My unhappy compromise was to just periodically repeat the thead - even though this is malformed HTML, it renders.