Error while installing FrontEndUsers module

[Swedane]

I am trying to get the Forum Module properly installed and active.

After installing it, I see the status "Missing Dependencies for Forum Module" shows
CMSMailer 1.73.9 True
and
CMS Made Simple™ 1.9.4.1 "Faanui"
but
FrontEndUsers 1.6 False
TreeManager 0.6 False

So I try to get and install the FrontEndUsers Module. I found FrontEndUsers 1.16.4, and try to install the FrontEndUsers-1.16.4.xml-file.

But then I get some errors:

ERROR: The CGExtensions module could not be found

Warning: Cannot modify header information - headers already sent by (output started at /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/modules/FrontEndUsers/FrontEndUsers.module.php:43) in /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/lib/classes/class.admintheme.inc.php on line 188

Warning: Cannot modify header information - headers already sent by (output started at /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/modules/FrontEndUsers/FrontEndUsers.module.php:43) in /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/lib/classes/class.admintheme.inc.php on line 191

Warning: Cannot modify header information - headers already sent by (output started at /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/modules/FrontEndUsers/FrontEndUsers.module.php:43) in /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/lib/classes/class.admintheme.inc.php on line 194

Warning: Cannot modify header information - headers already sent by (output started at /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/modules/FrontEndUsers/FrontEndUsers.module.php:43) in /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/lib/classes/class.admintheme.inc.php on line 195

Warning: Cannot modify header information - headers already sent by (output started at /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/modules/FrontEndUsers/FrontEndUsers.module.php:43) in /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/lib/classes/class.admintheme.inc.php on line 198

Warning: Cannot modify header information - headers already sent by (output started at /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/modules/FrontEndUsers/FrontEndUsers.module.php:43) in /mounted-storage/home63c/sub008/sc38991-KXHC/boo.bulderbyen.dk/cmsms/lib/classes/class.admintheme.inc.php on line 203

I can't understand what this means, and what I should do about it.
Can anyone here help?

Regards
Swedane

[staartmees]

you must first install CGExtensions before you can install the FEU-module. Also upgrade to at least cmsms 1.9.4.3 or 1.10.1