Got this error today:

sqlmap version: 1.0-dev-024c500
Python version: 2.6.6
Operating system: posix
Command line: sqlmap.py --random-agent --threads=10 --url=************************* --batch --crawl=3 --forms
Technique: UNION
Back-end DBMS: None (identified)
Traceback (most recent call last):
File "sqlmap.py", line 102, in main
start()
File "lib/controller/controller.py", line 503, in start
injection = checkSqlInjection(place, parameter, value)
File "lib/controller/checks.py", line 500, in checkSqlInjection
reqPayload, vector = unionTest(comment, place, parameter, value, prefix, suffix)
File "lib/techniques/union/test.py", line 308, in unionTest
validPayload, vector = _unionTestByCharBruteforce(comment, place, parameter, value, prefix, suffix)
File "lib/techniques/union/test.py", line 270, in _unionTestByCharBruteforce
validPayload, vector = _unionConfirm(comment, place, parameter, prefix, suffix, count)
File "lib/techniques/union/test.py", line 244, in _unionConfirm
validPayload, vector = _unionPosition(comment, place, parameter, prefix, suffix, count)
File "lib/techniques/union/test.py", line 182, in unionPosition
page, headers = Request.queryPage(payload, place=place, content=True, raise404=False)
File "lib/request/connect.py", line 1000, in queryPage
page, headers, code = Connect.getPage(url=uri, get=get, post=post, method=method, cookie=cookie, ua=ua, referer=referer, host=host, silent=silent, auxHeaders=auxHeaders, response=response, raise404=raise404, ignoreTimeout=timeBasedCompare)
File "lib/request/connect.py", line 597, in getPage
requestMsg = re.sub("(\n[A-Z]+ ).+?( HTTP/\d)", "\g<1>%s\g<2>" % getUnicode(), requestMsg, 1)
File "usr/lib64/python2.6/re.py", line 151, in sub
return _compile(pattern, 0).sub(repl, string, count)
File "usr/lib64/python2.6/re.py", line 278, in filter
return sre_parse.expand_template(template, match)
File "usr/lib64/python2.6/sre_parse.py", line 795, in expand_template
raise error, "invalid group reference"
error: invalid group reference