Invalid Argument Error

i can't reproduce this issue, all the importers are working just fine at my drupal installation!
try to change the path of the directory where the cookies are being stored since by default the cookie file is being stored in /var/tmp/ directory though that its kinda strange having yahoo working while the others aren't!! but just try to change this directory into another "writable" directory by your web server.
i will soon write a module configuration area for dcl_importer where you can change the cookies directory to what ever path you want and also it will contain other features.
i hope that this will work for your case, please send your feed back here and let us see what you'll have so we can fix this out if it was a bug!

actually no, you don't have to do a 'clean install' nor removing tables from your DB, the module should work just fine!
ok, lets start digging in that a step after another:
First, if there was any errors that PHP has generated while you were running the module then throwing them here would be very useful, to do that just type "error_reporting( E_ALL )" at the first line of dcl_wrapper.inc file, right after the tag "<?php"

Second, make sure that the directory {files/tmp} has a WRITE permission for your web server to create files and write on them in that directory, for example if you are using *NIX systems that would be something like "chmod 777 files/tmp" or whatever permission mod you prefer, just keep it "accessible" & "writable" by your web server.

Third, assuming your cookies directory is {files/tmp}, you should replace each occurrence for the string {/var/tmp/} by {files/tmp} in the following lines in each file:
(1) AOL --> ./modules/dcl_importer/scripts/importAol.class.php ( lines "84,87,88,186" )
(2) LYCOS --> ./modules/dcl_importer/scripts/importLycos.class.php ( line "76" )
(3) MYSPACE --> ./modules/dcl_importer/scripts/importMyspace.class.php ( lines "29,35" )
(4) YAHOO --> ./modules/dcl_importer/scripts/importYahoo.class.php ( line "44" )

try the above steps one by one, which means that you'll first give a shot to the first step, if it generated notices, warnings or errors then get back here and let us see them, if nothing has been thrown by PHP from the first step then go to the second one and make sure that everything is alright regarding your cookies directory and then do the changes on the target files as i have listed above "Third step" and run the module "keep the first step as it is and don't change it!"

let me know what you'll get!

My problem is with gmail only, and I have tested a yahoo.com account and that works fine. I have commented and followed the related thread at http://drupal.org/node/208874

Anyway, I did insert "error_reporting(E_ALL);" into the dcl_wrapper.inc file as suggested. I did not get any errors or notices in my error_log.
regarding the cookie directory, the importGmail.class.php file doesn't seem to contain a $cookieFile or point to /var/tmp/ so I wasn't able to test for cookie directory problems for gmail, but at least I know that yahoo works so it probably isn't a problem with the cookie in my situation.

Thanks.

just a fyi that this module uses copyrighted third party libraries (appears to be without permission) use at your own risk

I'm marking this issue as "won't fix". The D5 version of this module is no longer being maintained. The original version had scripts that no longer worked and some that weren't compatible with the GPL. The D6 version is being developed now and is a complete re-write using the OpenInviter library. If you wish to submit a backport to D5 I'll be happy to add that to CVS. Please see the project page for more details.