The following links explain those pesky Twitter Error Codes
I'm finding with a current program I'm developing that a 30 second delay between tweets seems to be acceptable, there could also be an issue if you continually send same message so try putting in a "loop count" value to vary the message for each tweet.
Has anyone found code to tweet the time of day as part of the tweet to produce a date/time stamp without actually having a RTC as a reference?
Regards