Just would like to note that I have been running into this issue with a suite of tests we have that work fine in firefox and chrome but not with iehta.

I have the same problem with win 2003/IE 6
with selenium-server-1.0-beta-1

I have got the same problem:

CONFIG:
Windows 2000 (with reg.exe in WINNT\SYSTEM32) + Internet Explorer 6 SP1

SELENIUM-VERSION: selenium-server-1.0-beta-1
In TestRunner.hta, access denied, line 1077, Char 9
SELENIUM-VERSION: selenium-server-1.0-SNAPSHOT-20081010.031134-802
In TestRunner.hta, access denied, line 1085, Char 9

COMMAND TO LAUNCH TEST SUITE:
java -jar selenium-server.jar -htmlSuite *iehta "http://test.application.de/" ".\tests\noproxy-nossl_suite.html" ".\results.html" -userExtensions ".\user-extensions.js"
--> with direct connection in IE Settings (no proxy)
---> also with the following proxy.pac:

function FindProxyForURL(url, host)
{
     if(shExpMatch(url, '/selenium-server/'))
          return "PROXY localhost:4444;"
     else
          return "DIRECT;"
}

OR WITH PROXY:
and -Dhttp.proxyHost=proxy -Dhttp.proxyPort=3128 option
...and new proxy.pac:

function FindProxyForURL(url, host)
{
     if(shExpMatch(url, '/selenium-server/'))
          return "PROXY localhost:4444; PROXY proxy.coconet.de:3128;"
     else if (shExpMatch(host, "*.domain.de"))
          return "DIRECT;"
     else if (shExpMatch(host, "*.domain.pl"))
          return "DIRECT;"
     else
          return "PROXY proxy:3128;"
}

...allways the same error

I tried "-proxyInjectionMode" and "-avoidProxy" but this leads to:

1) HtmlRunnerTestLoop is not defined
(line 141, character 1)
and
2) SeleniumHTARunner is not defined
(line 873, char 9)
3) and again to the error from above