I have added a 'Do Not cache theses websites rule', added the relevant websites and applied the rule. Now when i try to access these websites they crawl and take an eternity to display. If I disable the rule they then work perfectly again.
I followed the following rules from a MS KB article
Configure a cache rule
Configure a new cache rule to exclude a particular Web site's content from the cache. To do this, follow these steps:
Start the ISA Server Management tool.
Expand ServerName, where ServerName is the name of your ISA Server computer.
Expand Configuration, and then click Cache.
Do one of the following as appropriate for the version of ISA Server that you are running:
If you are running ISA Server 2006, click the Cache Rules tab, click the Tasks tab, and then click Create a Cache Rule.
If you are running ISA Server 2004, click the Tasks tab, and then click Create a Cache Rule.
Type a descriptive name for the new cache rule, and then click Next.
Click Add, click New, and then click Domain Name Set.
In the New Domain Name Set Policy Element dialog box, type a descriptive name for the policy element that will represent the domain that you do not want to cache content from.
Click Add, and then type the name of the domain that you do not want to cache content from. For example, type *.example.com.
Click OK, expand Domain Name Sets, click the new domain name set that you created, click Add, and then click Close.
Click Next, click Only if a valid version of the object exists in the cache. If no valid version exists, route the request to the server, and then click Next.
Click Never, no content will ever be cached, click Next, and then click Finish.
Click Apply to save your changes to the firewall policy, and then click OK.