Exchange / Outlook error "Unable to open your default e-mail folders"

I am unable to open users mailbox when using outlook. Error says “Unable to open your default e-mail folders. The Microsoft exchange server is not available”. Server pings by name and IP. OWA works fine. The event log below shows the error that is logged in event viewer on exchange server. No other users affected. This happens on multiple machines with this user. I have deleted the mail profile on the workstation and re-added several times. I have applied the suggested registry fix that increases the number of default concurrent MAPI sessions from 32 to 64 and this has not helped. This has happened in the past with other users and eventually the only thing that solved it was giving the user exchange admin privileges. Obviously this is not a permanent or feasible fix. Please help.

Event Type:       Error
Event Source:    MSExchangeIS
Event Category: General
Event ID:           9646
Date:                11/29/2007
Time:                2:06:23 PM
User:                N/A
Computer:         company-MAIL
Mapi session "/o=Company USA First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=cwardroup" exceeded the maximum of 32 objects of type "session".

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SembeeConnect With a Mentor Commented:
The TCP Chimney setting is a server setting. If you run the setting on Windows XP it will not work as the setting doesn't exist.

The setting change does require a server reboot.

It would also have helped if you pointed out that it was Exchange 2007 at the start.
The problem is caused by connections being dropped and not terminated correctly. The TCP Chimney issue causes that. Ensure that the network card drivers are up to date. If you haven't already, run the best practises tool from within the Toolbox.

Also note that Exchange 2007 Sp1 was released today.

The TCP Chimney issue is the current major issue and would be the first place I would look.

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patrickmillerAuthor Commented:
I have looked at the article that netmunky posted the link for and tried the steps they suggest even though I am running exchange 2007. I have also looked at the article that Sembee gave a link to but do not know if they are talking about disabling TCP chimney on the client or the server. I also have the problem on multiple clients/machines when trying to connect as this user, so I dont think this is a client side issue and thus my reluctance to disable TCP chimney. Thanks.
did you restart the information store service after increasing the maximum mapi sessions?
patrickmillerAuthor Commented:
I am reluctant to do so in the middle of the day, so I have not. I am also concerned that this will not deal with the root cause of why there are 32 open sessions in the first place and thus leave open the possibility that I will see this issue again down the road. This is tha 6th time we have seen this issue in teh last few weeks. In the past I have had to delete the mailbox to resolve this, and dont want to have to do that everytime. Thanks.  
how many users do you have on your mailserver?

not familiar with exchange 2007 so much, but i believe you should be able to see the current sessions in the system manager under First Storage Group -> Mailbox Store -> Logons
patrickmillerAuthor Commented:
could not find out how to view current sessions in EX 2007
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