Upgrading Drupal

Dear my friends I got an error after upgrading my drupal from 7.7 to 7.8. I researched it but I couldnt find anything. So I am here. Error is that

 Notice: unserialize() [function.unserialize]: Error at offset 2 of 25 bytes in variable_initialize() (line 916 of /home/******/public_html/includes/bootstrap.inc).
Notice: unserialize() [function.unserialize]: Error at offset 20 of 26 bytes in variable_initialize() (line 916 of /home/******/public_html/includes/bootstrap.inc). 

And that is the line 916

When I migrate to Drupal 7 how much of a laptop is recommended to run everything locally?

Thanks

Hi, I'm planning to do my first securitty update of Drupal 6. I decided to backup my site on a subdomain first. So I:

- Copied all files and folders from the live site to the 'backup' subdomain
- added a new database called 'backup'
- imported the database
- changed setting.php to point to the new database.

All my user facing pages are working fine however when I try to access the administration page or any other configuration/building page e.g. views, modules, etc it takes ages to load then results with an error which looks as long as my database. I haven't copied it all but the first part is as follows:

I just upgraded my Drupal site with the Calendar module to Drupal 7.8. I upgraded the Date, Chaos Tools, Views, and Calendar modules to the latest versions.

The problems I'm having are:
1. I can get to the admin screens, but the home page (supposed to show the Calendar) has a Page Not Found error.

2. When I go to edit the view for the calendar, I get an error :Fatal error: Call to a member function get_option() on a non-object in /var/www/drupal7/sites/all/modules/views/plugins/views_plugin_style.inc on line 41

Tried to update from 7.7 to 7.8, download the file. Added it to the site but error of the file being to big therefore unable to update?.. I apologise, I'm a new person to this site and have little knowledge of what to do. Could anyone please advise?.

I have a local install on Windows to learn to use Drupal - I mostly use Joomla! and WordPress. I have to do a minor update.

I have looked at the documentation wiki and forum and this seems to be effectively a re-install fraught with all sorts of backup problems. Is there no "update" button as with other CMS systems (Joomla!, WordPress etc)?

Is the only option to effectively rip out what I have done so far, delete the old Drupal, install the new and then re-install everything from the database upwards (hoping it all works)?