Intermittent "Request header field is missing ':' separator." on https

[Michael Cole <michaelcole@xxxxxxxxxxxxxxx>]

Hello,

I'm trying to resolve a problem with intermittent "Bad Request" errors from apache:

     Bad Request

     Your browser sent a request that this server could not understand.

     Request header field is missing ':' separator.

     olhuaqv3o1t29flvr0

     Apache/2.2.14 (Ubuntu) Server at xxx.net Port 443

These Bad Requests only happen with https (SSL cert from godaddy.com).  Regular http doesn't show this problem.  They are happening on both IE and Firefox.

They showed up out of nowhere last friday (of course after I emailed a URL to a client :-)

These "Bad Request" responses come back intermittently.  I've checked that the "good" requests are exactly the same as the "bad" ones with Firebug.  This is an example of a form POST, but it also happens on page GETs.

  Here is an example of the request:
  POST /index.php HTTP/1.1
  Host: xxx.net
  User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.8) Gecko/20100723 Ubuntu/10.04 (lucid) Firefox/3.6.8

  Accept: text/_javascript_, text/html, application/xml, text/xml, */*
  Accept-Language: en-us,en;q=0.5
  Accept-Encoding: gzip,deflate
  Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
  Keep-Alive: 115
  Connection: keep-alive

  X-Requested-With: XMLHttpRequest
  X-Prototype-Version: 1.6.0.3
  Content-Type: application/x-www-form-urlencoded; charset=UTF-8
  Referer: https://xxx.net/index.php?controller=User&action="">

  Content-Length: 44
  Cookie: secorix=i4dq7b23gcgf8trrprr6ieq5j5
  Pragma: no-cache
  Cache-Control: no-cache

The server is hosted by Amazon Web services, and is Ubuntu 10.04's standard server distribution.  $ dpkg -l '*apache*'

ii  apache2                                       2.2.14-5ubuntu8                               Apache HTTP Server metapackage
ii  apache2-mpm-prefork                           2.2.14-5ubuntu8                               Apache HTTP Server - traditional non-threaded model

ii  apache2-threaded-dev                          2.2.14-5ubuntu8                               Apache development headers - threaded MPM
ii  apache2-utils                                 2.2.14-5ubuntu8                               utility programs for webservers

ii  apache2.2-bin                                 2.2.14-5ubuntu8                               Apache HTTP Server common binary files
ii  apache2.2-common                              2.2.14-5ubuntu8                               Apache HTTP Server common files

ii  libapache2-svn                                1.6.6dfsg-2ubuntu1                            Subversion server modules for Apache

From the error log, I get these errors (intermixed with everything else):

[Mon Aug 30 21:27:06 2010] [warn] Init: Name-based SSL virtual hosts only work for clients with TLS server name indication support (RFC 4366)
[Mon Aug 30 21:27:06 2010] [notice] Apache/2.2.14 (Ubuntu) DAV/2 SVN/1.6.6 PHP/5.3.2-1ubuntu4.2 with Suhosin-Patch mod_ssl/2.2.14 OpenSSL/0.9.8k configured -- resuming normal operations

[Mon Aug 30 18:04:53 2010] [error] Hostname xxx.net provided via SNI, but no hostname provided in HTTP request
[Mon Aug 30 21:28:15 2010] [error] [client 64.71.7.18] request failed: error reading the headers

[Mon Aug 30 21:53:42 2010] [error] [client 64.71.7.18] request failed: error reading the headers, referer: https://xxx.net/index.php?controller=User&action="">

I've been searching forums all day but haven't found any fixes.  Reset browser cookies, and checked for proxies.  Any advice?

Thanks in advance,

Mike