WIndows 2000 Server/ISA 2000 Update Err 0x8024401B Work around

I've had this windows update problem for an age and have applied all the
recommended patches to ISA but the only way I can get my Windows 2000 SP4
Serves to update is to clear the ISA servers cache each time I update a
server.

To clear the ISA servers cache

Expand - 'cache configuration'
Select - 'Drives' and set the the Maximum Cache Size to 0, click OK
Choose option save changes and restart services.

wait for services to restart then repeat above setting your cache back to
previous level

Update your server.