Select boxes and "Could not convert JavaScript argument" (NS_ERROR_XPC_BAD_CONVERT_JS)

While trying to add a dynamically generated option to a select box I ran into this error:

Error: uncaught exception: [Exception... "Could not convert JavaScript argument" nsresult: "0x80570009 (NS_ERROR_XPC_BAD_CONVERT_JS)" location: "JS frame :: file:///C:/Documents%20and%20Settings/mmbmb/Desktop/calendar%20de3v/calendarDateInput.js :: PickDisplayDay :: line 148" data: no]

I was perplexed for some time until I did a little research and ran into this page on Quirksmode. The solution lies here:

 for(i=0;i

I was trying to call the .add method of a select using text as an argument. This is non-standard (but I think works in IE). You have to instantiate an option object or else JS will error while trying to convert. Quirksmode is great btw.