Error during connection to (64) or (53)

Hey everyone

I have a SCCM 2007 R3 site with multiple Secondary Sites. All other Sites are functioning fine, however sending packages to one site in particular has been problematic. It worked up until a week or so ago.

From the primary site server, I can ping and nslookup the secondary site server

From the secondary site server, I can ping and nslookup the primary site server

On the secondary site server, I have the primary site server computer account in the local administrator's group

I made sure all the SMS shares on the Secondary site are still available and present.

I checked permissions on the Site Server's SMSPKGC$ directory, and the administrators group is populated with Full Control (which contains an AD group containing my primary site server computer account)

The sender account for the Secondary site contains the correct DNS name for the Secondary Site Server

I've tried removing the problematic package and re-sending = no luck

I've tried sending a new, smaller test package = no luck

In the Sender.log on the Primary Site Server, I see these errors:

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Error during connection to  \\SecondarySiteServer.domain.com\SMS_SITE (64).

Error during connection to \\SecondarySiteServer\SMS_SITE (64).

Error during connection to \\SecondarySiteServer\SMS_Site (53).

Cannot connect to server SecondarySiteServer at remote site <Site #>, won't try send requests going to site <SecondarySite#> for an hour or until there are not active send requests.

FQDN for server SecondarySiteServer is SecondarySiteServer.domain.com

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I'm seeing both 53 & 64 errors.

I did notice on the Secondary Site server that I get occasional MP check failures in the MPCONTROL.log:

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Call to HttpSendRequestSync succeeded for port 80 with status code 200, text:OK

Http test request succeeded.

Successfully performed Management point availability check against local computer.

Call to HttpSendRequestSync failed for port 80 with status code 500, text: Internal Server Error

Http test request failed, status code is 500, 'Internal Server Error'

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Does anyone have any recommendations on what to check for next?

Thanks