Boost won't work after configuration of .HTaccess Preliminary data

It seems I've configured .HTaccess right, as required by the following guide to installing Boost, But it also seems the module doesn't work.

What I did was to copy my .HTaccess auto generated rules from admin/config/system/boost/htaccess/generator and paste it exactly instead of the sentence "-------paste the rules right here--------" mentioned above, but I don't know if that was the true intention of the author...

Anyway, the final outcome is this:

# RewriteBase /

### BOOST START ###

# Allow for alt paths to be set via htaccess rules; allows for cached variants (future mobile support)   
RewriteRule .* - [E=boostpath:normal]

# Caching for anonymous users   # Skip boost IF not get request OR uri has wrong dir OR cookie is set OR request came from this server OR https request   
RewriteCond %{REQUEST_METHOD} !^(GET|HEAD)$ [OR]   
RewriteCond %{REQUEST_URI} (^/(admin|cache|misc|modules|sites|system|openid|themes|node/add|comment/reply))|(/(edit|user|user/(login|password|register))$) [OR]   
RewriteCond %{HTTPS} on [OR]   
RewriteCond %{HTTP_COOKIE} DRUPAL_UID [OR]   
RewriteCond %{ENV:REDIRECT_STATUS} 200   
RewriteRule .* - [S=3]

# GZIP   
RewriteCond %{HTTP:Accept-encoding} !gzip   
RewriteRule .* - [S=1]   
RewriteCond %{DOCUMENT_ROOT}/cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html\.gz -s   
RewriteRule .* cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html\.gz [L,T=text/html,E=no-gzip:1]

# NORMAL   
RewriteCond %{DOCUMENT_ROOT}/cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html -s   
RewriteRule .* cache/%{ENV:boostpath}/%{HTTP_HOST}%{REQUEST_URI}_%{QUERY_STRING}\.html [L,T=text/html]

### BOOST END ###

# Rewrite URLs of the form 'x' to the form 'index.php?q=x'.
# Pass all requests not referring directly to files in the filesystem to
# index.php. Clean URLs are handled in drupal_environment_initialize().
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !=/favicon.ico
RewriteRule ^ index.php [L]


Why I'm assuming a problem?

On one hand, Drupal's CRON tells me Boost installed correctly, should be working if properly configured. On second hand, while surfing from another browser anonymously, I checked page source (CTRL+U), But didn't the famous message (as HTML note): 


  Page cached by Boost @ YYYY-MM-DD HH:MM:SS, expires @ YYYY-MM-DD
  HH:MM:SS, lifetime X hours


Therefore, I assume a problem. Now, as Shawn instructed in the comments below, I turned on the Boost debugger, went to Reports > Recent log messages, and then saw two interesting errors:

First error:

Array
(
    [cache_this] =&gt;
)


Second error:

This error is to long to be pasted here, but it seems to do something with Drupal's Autocomplete mechanism.
You can verify Boost is working by browsing a page as an anonymous user (e.g. using your browser's Incognito/Private Browsing mode) and looking at the source code of the page. If Boost is working you should see a HTML comment at the bottom of the document that looks like this:

&lt;!-- Page cached by Boost @ YYYY-MM-DD HH:MM:SS, expires @ YYYY-MM-DD HH:MM:SS, lifetime X hours --&gt;