Fixing error messages!

[Tantrwm]

I'm trying to set up an installation of OS Commerce (this is my first time so bear with me!)... it was installed directly by my service provider so i don't know a great deal about it's workings yet. Have followed the documentation all through the setting up and added a product, but when i look at my shop i have an error appearing in the top left corner of the page (using default template for the time being).

 

The error is as follows:

 

Warning: fread() [function.fread]: Length parameter must be greater than 0. in /mydomain/includes/functions/cache.php on line 60

 

I've tried looking in the file that it mentions but i can't see the function it refers to, nor do i know where the parameter is coming from in order to change it to something other than 0.... ? Can anyone help with this?

 

Also I am getting an error on the backups page:

 Error: Backup directory does not exist. Please set this in configure.php.

 

But the backup directory that the install has listed for this is the wrong path. How do i change this setting? and where is configure.php?

 

I would be grateful for any help, still don't know my way around OSCommerce, it's quite confusing and overwhelming at this stage!