Here's another alternative.
Come up with a search that targets only the cases you want to close.
Then, generate an API token using this process:
http://blog.fogcreek.com/an-api-tutorial-plus-excel-2007-export-plus-zombies/
Send both along to us, and we'll close the cases in bulk with a handy script. After we're done, we'll log out that token so that it's no longer usable.
Or, if you can run python scripts, you can do it yourself with the FogBugzPy library:
https://developers.kilnhg.com/Code/FogBugz/Group/FogBugzPy
import re, string, sys, time,os,cgi
from fogbugz import FogBugz
the_search = 'tag:oops'
the_client = 'https://foo.fogbugz.com'
the_token = 'mytoken'
fogbugz = FogBugz(the_client,the_token)
old_cases = fogbugz.search(q=the_search,cols="ixBug,fOpen")
for case in old_cases.cases.childGenerator():
fogbugz.resolve(ixBug=case.ixbug.string)
fogbugz.close(ixBug=case.ixbug.string)