First things first, what I'm trying to do works on any off-line test system I have including a recent backup of the live system which s why I think it's the host ISP's system but need help in proving it.

Initially the error window looked like a script and then I discovered it was the Google Tracking script so I deleted that and the error message changed to plain text and interestingly I can't add the google snippet back now as it will give the same error as a HTML block with script.

When this error happens if you try more than once the site crashes and takes about 10 minutes to recover. The host system uses CPanel for back end admin and it crashes at the same time or is possibly the cause of the crash?

The Error window now says "Page Not Found No page could be found at this address. Back to Home"

The system environment is

# concrete5 Version
5.6.3.5

# concrete5 Packages
Add Multiple Pages (2.1.1), Advanced Page List (1.0.3), Amiant CSS3 Menu (0.3), City5 Carousel (0.9.7), CSS3 Button (1.1), CSV displayer (1.2), Deluxe Image Gallery (1.6.6), Designer Content (3.1.1), Dynamic Iframe (1.7), File Templates+ (0.2), Google Docs Viewer (1.0), Hutman News (3.0.1.2), Iframe (1.0), Instant JavaScript (1.0.1), List files from set (1.0.4), Magic Tabs (2.0.2), Page Hit Counter (1.1), Page List Title (2.3), Page Redirect (1.4), Page Selector Attribute (1.1), PC5 Custom Templates (3.5), PDF Viewer (1.1), Scrapbook Display - Basic (1.4), Search Block Templates (1.0), Simple Image Gallery (1.1.3), Slate Theme (1.5.3.1), Social Timeline (1.2), Sticker (1.0), Ticker (1.0.1), tnSpacer (1.3), Whale Nivo Image Slider (1.2), Where Is My Block? (1.1), Zoom Image (1.0.5).

# concrete5 Overrides
blocks/css_lightbox, blocks/footer_back_to_top, blocks/autonav, blocks/page_list, blocks/image_pop, blocks/shadow_on_block, blocks/block_shadow_n_scale, js/switch.js, languages/zh_TW, languages/it_IT, languages/sk_SK, languages/nl_NL, languages/cs_CZ, languages/da_DK, languages/el_GR, languages/es_PE, languages/de_DE, languages/fr_FR, languages/es_AR, languages/fi_FI, languages/fa_IR, languages/ar, languages/zh_CN, languages/es_ES, languages/he_IL, languages/ru_RU, languages/nb_NO, languages/sl_SI, languages/tr_TR, languages/pt_PT, languages/es_MX, languages/ro_RO, languages/sv_SE, languages/vi_VN, languages/ja_JP, themes/theme_ambertech, themes/theme_amber_2

# concrete5 Cache Settings
Block Cache - On
Overrides Cache - On
Full Page Caching - Off

# Server Software
Apache

# Server API
cgi-fcgi

# PHP Version
5.6.33

# PHP Extensions
bcmath, bz2, bz2_filter, calendar, cgi-fcgi, Core, ctype, curl, date, dom, ereg, exif, filter, ftp, gd, gettext, gmp, hash, iconv, imap, jsmin, json, libxml, mbstring, mcrypt, mhash, mysql, mysqli, openssl, pcntl, pcre, PDO, pdo_mysql, pdo_sqlite, Phar, posix, pspell, readline, Reflection, session, shmop, SimpleXML, soap, sockets, SPL, sqlite3, standard, tokenizer, xml, xmlreader, xmlwriter, zip, zlib.

# PHP Settings
max_execution_time - 30
log_errors_max_len - 1024
max_file_uploads - 20
max_input_nesting_level - 64
max_input_time - -1
max_input_vars - 1000
memory_limit - 512M
post_max_size - 128M
sql.safe_mode - Off
upload_max_filesize - 1G
mysql.max_links - Unlimited
mysql.max_persistent - Unlimited
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
session.cache_limiter - nocache
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5

Any help would be greatly appreciated
Cheers
Ralph