Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content.

After Adding a new index server to the farm - made that a dedicated indexer-

after that when I tried a full crawl the crawl stopped immediately and the following error is recorded to crawl log:

Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content.

also, on the indexer windows event log there was this warnings:

event id :2436  The start address cannot be crawled. Context: Application 'SharedServices1', Catalog 'Portal_Content'  Details:   Access is denied. Check that the Default Content Access Account has access to this content, or add a crawl rule to crawl this content.   (0x80041205)

So I googled and find this brilliant forum topic on msdn

http://social.technet.microsoft.com/Forums/en-US/sharepointsearch/thread/52877c8f-ac38-4cd3-813e-87f8f7a6882f

Applied the solution and it worked like a charm.

1.    Click Start, click Run, type regedit, and then click OK.
2.    In Registry Editor, locate and then click the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
3.    Right-click Lsa, point to New, and then click DWORD Value.
4.    Type DisableLoopbackCheck, and then press ENTER.
5.    Right-click DisableLoopbackCheck, and then click Modify.
6.    In the Value data box, type 1, and then click OK.
7.    Quit Registry Editor, and then restart your computer.

Can be seen on the screenshot..