navigating to a server alias from itself prompts for credentials - Windows Server 2008 R2

Hi

I have 2 virtual Windows Server 2008 R2 machines.

I use Radware technology to have NLB between those servers. so there's an alias for those servers

when I navigate to \\alias from workstations everything works great.

when I navigate to \\alias from the servers themselves I'm prompted to enter credentials.

doesn't matter what credentials I'm trying to enter - no luck... not sure what credentials it asks for but when I navigate to\\server1 from server1 I get the shares without any problem

I tried the following registry keys with restarting the machine but they didn't affect anything:

DisableLoopbackCheck=1

2. HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters
DisableStrictNameChecking=1

I tried to access with FQDN instead of NetBIOS name with no luck

I tried add with serviceprincipalname for the server's account:
Setspn -S HOST\Alias ;  Setspn -S HOST\Alias.fqdn

again... no luck

what am I doing wrong? :(

btw the servers are almost identical. both use for the same purpose and have the IIS Role installed

please help

Tamir Levy