Token/Login intermittently returns either error 8 or error 1003

Let me get you some background on how and what we are doing. This is running on C#.

Scenario: Rename Unit , Update a CustomField, Update ProfileField in sequential operation.
This is the sequence of actions are:

1)    “token/login” to obtain SID
2)     “item/update_name”
3)    “token/login” to obtain SID
4)    “item/update_profile_field”
5)    “token/login” to obtain SID
6)    “item/update_custom_field”

Concurrently, there is another machine that queries Unit data every 5 minutes using the same account.
The sequence of actions for that are:

1)    “token/login” to obtain SID
2)    “core/search_items” for the Units

The problem I’m having is during the “token/login” call on my “Update” operation.

I'm getting either:

{"error":8, "reason":"INVALID_AUHT_TOKEN"}

or

{"error":1003, "reason":"LIMIT invalid_logins"}

If I retry it a couple of time, then it will be fine.

Any idea why?

could the 2 machines using the same account has any bearing on this? (i did try to run my "update" operation while the "query" is not running but still getting the either error 8 or 1003).

Is there a limit on how many queries i can make within a time limit?

Regards,

Anson