Problem after upgrade to 1.11.7 with being logged out

[streever]

Hello,

my admin account gets logged out, seemingly at random, as I try to use the site post upgrade to 1.11.7.

I've checked sessions: the server is capable of making them & there seems nothing consistent about the log outs. It happens often in 3rd party modules, but also when I browse the pages or the system section.

I've forced (via .htaccess) the full domain, including www, whenever the site is used. That doesn't seem to have actually improved the situation: we are still randomly logged out at times.

I pass the md5 checksum, no files are missing or incorrect.

My database checks out as ok when I run checks on it.

I have cookies on my machine from the site.

I'm using the Chrome browser, but it occurs when I tried to use Internet Explorer & Firefox as well.

It MOSTLY seems to happen after I submit a form. If I "Apply" an update to a page, everything is fine. If I "Submit" and it tries to load the pages list, it logs me out instead.

My base url in config.php is http://www.ctlandmarks.org

My .htaccess rule is:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^ctlandmarks.org [NC]
RewriteRule ^(.*)$ http://www.ctlandmarks.org/$1 [L,R=301,NC]

The following functions are DISABLED according to system information, with a Yellow exclamation mark, but I have no idea which ones are relevant--if any:
dl, exec, passthru, shell_exec, system, proc_open, proc_close, popen, show_source, symlink, escapeshellarg, escapeshellcmd, php_uname

Any ideas?

My system information follows:
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Cms Version: 1.11.7

Installed Modules:

CMSMailer: 5.2.1
FileManager: 1.4.3
MenuManager: 1.8.5
ModuleManager: 1.5.5
News: 2.12.12
Printing: 0.2.6
Search: 1.7.8
ThemeManager: 1.1.8
TinyMCE: 2.9.12
CGExtensions: 1.36
FormBuilder: 0.5.2
FrontEndUsers: 1.4.2
CustomContent: 1.5
CMSPrinting: 1.0.4
CGCalendar: 1.10.4

Config Information:

php_memory_limit:
process_whole_template:
max_upload_size: 25000000
url_rewriting: none
page_extension:
query_var: page
image_manipulation_prog: GD
auto_alias_content: true
locale:
default_encoding:
admin_encoding: utf-8
set_names: true

Php Information:

phpversion: 5.3.25
md5_function: On (True)
gd_version: 2
tempnam_function: On (True)
magic_quotes_runtime: Off (False)
E_STRICT: 0
E_DEPRECATED: 0
memory_limit: 128M
max_execution_time: 60
output_buffering: 4096
safe_mode: Off (False)
file_uploads: On (True)
post_max_size: 25M
upload_max_filesize: 25M
session_save_path: /tmp (0700)
session_use_cookies: On (True)
xml_function: On (True)
xmlreader_class: On (True)

Server Information:

Server Api: cgi-fcgi
Server Db Type: MySQL (mysql)
Server Db Version: 5.5.31
Server Db Grants: Found a "GRANT ALL" statement that appears to be suitable

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