Garmin problem "activity is undefined"

Can you be specific about what you mean by "unload and reload the communicator"? 

One thing to be aware of is that Training Center doesn't use Garmin Communicator. Communicator is for interfacing to the web. So you've most likely eliminated the possibility of problems with the 405 itself. 

Next time this happens, before doing anything else, try going to this Garmin Test page, then select TCX History (all)  and click Read From Device. That can help us determine if the problem is in the Garmin code or the BT code.

I reinstalled the communicator yesterday.  Even though I have the 405, I installed the older communicator.  I think I have had this problem with bothe versions though.  I was able to upload the workout that wouldn't originally go, and a new one.  I did the test page just now and got this:

Part Number:        006-B0717-00
Software Version:    230
Description:        Forerunner 405 Software Version 2.30
Id:            3478661629

-DataType---------------
  Name:        GPSData
  Extension:    GPX
  Read:        true
  Write:    true

-DataType---------------
  Name:        FitnessHistory
  Extension:    TCX
  Read:        true
  Write:    false

-DataType---------------
  Name:        FitnessUserProfile
  Extension:    TCX
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessNewLeaf
  Extension:    NLF
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessActivityGoals
  Extension:    TCX
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessCourses
  Extension:    TCX
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessWorkouts
  Extension:    TCX
  Read:        false
  Write:    true

I just got the error again       TypeError: activity is undefined

I ran the test page and got this:
Part Number:        006-B0717-00
Software Version:    230
Description:        Forerunner 405 Software Version 2.30
Id:            3478661629

-DataType---------------
  Name:        GPSData
  Extension:    GPX
  Read:        true
  Write:    true

-DataType---------------
  Name:        FitnessHistory
  Extension:    TCX
  Read:        true
  Write:    false

-DataType---------------
  Name:        FitnessUserProfile
  Extension:    TCX
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessNewLeaf
  Extension:    NLF
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessActivityGoals
  Extension:    TCX
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessCourses
  Extension:    TCX
  Read:        false
  Write:    true

-DataType---------------
  Name:        FitnessWorkouts
  Extension:    TCX
  Read:        false
  Write:    true

I hope this helps

When this happens, can you do the second part of the test?
Under File Type, select TCX History (all)  and then click Read From Device.

It did it again, so I ran the test page as you asked.  I got an error that said this:

Error: ERROR: Unable to parse TCX document.

So I'm guessing it's a Garmin problem and I will call them right?

Ok, that's what I expected to see.

Before you call Garmin support: have you been deleting workouts from the unit? If you don't, once it gets full it will degrade the data on the unit to store new data. This is to prevent the unit from freezing up. While it handles this situation pretty elegantly eventually you can end up with some strange behavior when trying to use data off of the device. 

If you haven't deleted data from the unit before, try deleting anything over one month old then record a new workout and see what happens.

Of course, if you have been clearing old data off of the device it's definitely time to call Garmin.