diff --git a/cps/cache_buster.py b/cps/cache_buster.py
index 9619d605..ba19afd6 100644
--- a/cps/cache_buster.py
+++ b/cps/cache_buster.py
@@ -47,13 +47,16 @@ def init_cache_busting(app):
         for filename in filenames:
             # compute version component
             rooted_filename = os.path.join(dirpath, filename)
-            with open(rooted_filename, 'rb') as f:
-                file_hash = hashlib.md5(f.read()).hexdigest()[:7] # nosec
+            try:
+                with open(rooted_filename, 'rb') as f:
+                    file_hash = hashlib.md5(f.read()).hexdigest()[:7] # nosec
+                # save version to tables
+                file_path = rooted_filename.replace(static_folder, "")
+                file_path = file_path.replace("\\", "/")  # Convert Windows path to web path
+                hash_table[file_path] = file_hash
+            except PermissionError:
+                log.error("No permission to access {} file.".format(rooted_filename))
 
-            # save version to tables
-            file_path = rooted_filename.replace(static_folder, "")
-            file_path = file_path.replace("\\", "/")  # Convert Windows path to web path
-            hash_table[file_path] = file_hash
     log.debug('Finished computing cache-busting values')
 
     def bust_filename(filename):
diff --git a/cps/constants.py b/cps/constants.py
index c2eb0527..f40d16b0 100644
--- a/cps/constants.py
+++ b/cps/constants.py
@@ -154,7 +154,7 @@ def selected_roles(dictionary):
 BookMeta = namedtuple('BookMeta', 'file_path, extension, title, author, cover, description, tags, series, '
                                   'series_id, languages, publisher')
 
-STABLE_VERSION = {'version': '0.6.18'}
+STABLE_VERSION = {'version': '0.6.19 Beta'}
 
 NIGHTLY_VERSION = dict()
 NIGHTLY_VERSION[0] = '$Format:%H$'
diff --git a/cps/error_handler.py b/cps/error_handler.py
index 37b7500e..67252a66 100644
--- a/cps/error_handler.py
+++ b/cps/error_handler.py
@@ -42,8 +42,9 @@ def error_http(error):
 
 def internal_error(error):
     return render_template('http_error.html',
-                           error_code="Internal Server Error",
-                           error_name=str(error),
+                           error_code="500 Internal Server Error",
+                           error_name='The server encountered an internal error and was unable to complete your '
+                                      'request. There is an error in the application.',
                            issue=True,
                            unconfigured=False,
                            error_stack=traceback.format_exc().split("\n"),
diff --git a/cps/helper.py b/cps/helper.py
index 742188d0..5d5cc021 100644
--- a/cps/helper.py
+++ b/cps/helper.py
@@ -698,9 +698,12 @@ def delete_book(book, calibrepath, book_format):
 
 def get_cover_on_failure(use_generic_cover):
     if use_generic_cover:
-        return send_from_directory(_STATIC_DIR, "generic_cover.jpg")
-    else:
-        return None
+        try:
+            return send_from_directory(_STATIC_DIR, "generic_cover.jpg")
+        except PermissionError:
+            log.error("No permission to access generic_cover.jpg file.")
+            abort(403)
+    abort(404)
 
 
 def get_book_cover(book_id):
diff --git a/cps/render_template.py b/cps/render_template.py
index 0c5423c9..d2f40d6c 100644
--- a/cps/render_template.py
+++ b/cps/render_template.py
@@ -18,11 +18,11 @@
 
 from flask import render_template, request
 from flask_babel import gettext as _
-from flask import g
+from flask import g, abort
 from werkzeug.local import LocalProxy
 from flask_login import current_user
 
-from . import config, constants, ub, logger, db, calibre_db
+from . import config, constants, logger
 from .ub import User
 
 
@@ -119,6 +119,10 @@ def get_sidebar_config(kwargs=None):
 # Returns the template for rendering and includes the instance name
 def render_title_template(*args, **kwargs):
     sidebar, simple = get_sidebar_config(kwargs)
-    return render_template(instance=config.config_calibre_web_title, sidebar=sidebar, simple=simple,
-                           accept=constants.EXTENSIONS_UPLOAD, # read_book_ids=get_readbooks_ids(),
-                           *args, **kwargs)
+    try:
+        return render_template(instance=config.config_calibre_web_title, sidebar=sidebar, simple=simple,
+                               accept=constants.EXTENSIONS_UPLOAD,
+                               *args, **kwargs)
+    except PermissionError:
+        log.error("No permission to access {} file.".format(args[0]))
+        abort(403)
diff --git a/cps/web.py b/cps/web.py
index e8bf48e3..a0ecbb8e 100644
--- a/cps/web.py
+++ b/cps/web.py
@@ -1368,7 +1368,11 @@ def get_cover(book_id):
 
 @web.route("/robots.txt")
 def get_robots():
-    return send_from_directory(constants.STATIC_DIR, "robots.txt")
+    try:
+        return send_from_directory(constants.STATIC_DIR, "robots.txt")
+    except PermissionError:
+        log.error("No permission to access robots.txt file.")
+        abort(403)
 
 
 @web.route("/show/<int:book_id>/<book_format>", defaults={'anyname': 'None'})