I just upgraded Firefox to version 3.0, and tried to export a collection of items as I used with Zotero on FF2 (same Zotero version, same items) to BibTeX format. However, I got this error message: "An error occurred while trying to export the select". Reviewing the resulting BibTeX file, I see it ends in the middle of a record, just before writing "pages" data:

@book{hempel_aspects_1965,
        address = {New York},
        title = {Aspects of Scientific Explanation, and Other Essays in the Philosophy of Science},
        publisher = {The Free Press},
        author = {C. G. Hempel},
        year = {1965},
        keywords = {Ciencia,Filosofía},

This coincides with message in Firefox JS Error Console:

Error: item.pages.replace is not a function
Source File: chrome://zotero/content/xpcom/translate.js
Line: 2463

After seeing this I deleted and replaced Pages data of this item, and tried the export again, this time exporting was successful.

However, when I compare Zotero RDF export of problematic and unproblematic item, I cannot see any difference related to pages:

$ diff /tmp/Hempel/Hempel.rdf /tmp/Hempel1/Hempel1.rdf 
12,21c12
<   <vcard:Address RDF:about="rdf:#$61c4+1"
<                    vcard:locality="New York" />
<   <RDF:Seq RDF:about="rdf:#$31c4+1">
<     <RDF:li RDF:resource="rdf:#$21c4+1"/>
<   </RDF:Seq>
<   <z:AutomaticTag RDF:about="rdf:#$51c4+1"
<                    RDF:value="Filosofía" />
<   <z:AutomaticTag RDF:about="rdf:#$41c4+1"
<                    RDF:value="Ciencia" />
<   <dcterms:LCC RDF:about="rdf:#$71c4+1"
---
>   <dcterms:LCC RDF:about="rdf:#$e1c4+1"
22a14,20
>   <foaf:Organization RDF:about="rdf:#$81c4+1"
>                    foaf:name="The Free Press">
>     <vcard:adr RDF:resource="rdf:#$d1c4+1"/>
>   </foaf:Organization>
>   <foaf:Person RDF:about="rdf:#$91c4+1"
>                    foaf:surname="Hempel"
>                    foaf:givenname="C. G." />
29,33c27,31
<     <dc:publisher RDF:resource="rdf:#$11c4+1"/>
<     <bib:authors RDF:resource="rdf:#$31c4+1"/>
<     <dc:subject RDF:resource="rdf:#$41c4+1"/>
<     <dc:subject RDF:resource="rdf:#$51c4+1"/>
<     <dc:subject RDF:resource="rdf:#$71c4+1"/>
---
>     <dc:publisher RDF:resource="rdf:#$81c4+1"/>
>     <bib:authors RDF:resource="rdf:#$a1c4+1"/>
>     <dc:subject RDF:resource="rdf:#$b1c4+1"/>
>     <dc:subject RDF:resource="rdf:#$c1c4+1"/>
>     <dc:subject RDF:resource="rdf:#$e1c4+1"/>
35,41c33,41
<   <foaf:Organization RDF:about="rdf:#$11c4+1"
<                    foaf:name="The Free Press">
<     <vcard:adr RDF:resource="rdf:#$61c4+1"/>
<   </foaf:Organization>
<   <foaf:Person RDF:about="rdf:#$21c4+1"
<                    foaf:surname="Hempel"
<                    foaf:givenname="C. G." />
---
>   <z:AutomaticTag RDF:about="rdf:#$b1c4+1"
>                    RDF:value="Ciencia" />
>   <vcard:Address RDF:about="rdf:#$d1c4+1"
>                    vcard:locality="New York" />
>   <RDF:Seq RDF:about="rdf:#$a1c4+1">
>     <RDF:li RDF:resource="rdf:#$91c4+1"/>
>   </RDF:Seq>
>   <z:AutomaticTag RDF:about="rdf:#$c1c4+1"
>                    RDF:value="Filosofía" />

I hope this info to be useful to fix any problem related to Zotero. If you require complete RDF files, please just ask.