Your comments

A B wrote: "All goods, but the power is displayed in kWh not kW."

That's not true. 

http://en.wikipedia.org/wiki/Power_(physics)#Units
"The SI unit of power is the watt (W)." 

http://en.wikipedia.org/wiki/Units_of_energy#Electricity
"The energy unit used for everyday electricity, particularly for utility bills, is the kilowatt-hour (kWh)."
I'm aware of that the temperature value reported by telldus server should be multiplied by 10.
Strictly speaking the energy meter reports the correct number of blinks pr. one minute.
Telldus' server processes this value as a temperature value in "Fine Offset" format, hence dividing it by 10.
Why are you multiplying by 60?
One Wh pr. blink is one Wh pr. blink regardless of the sample interval.
24 blinks represents 24 Wh regardless of sample interval.
It's only when calculating the average power you have to take the sample interval into account.
24 Wh gives 24*3600 = 86400 Ws or 1440 Watt minutes if you wish.
86400 Ws during 60 seconds gives an average power of 86400/60 = 1440 W or 1,44 kW.
This is value I expect to see in the graph.
Now tellmon.net works ok as well. Thank you!
If we assume 1 "blink" per Wh, then adding the blinks will result in the consumed energy i Wh. To display in kWh you have to divide by 1000. (Adding the average Wh values will not give the correct result, you have to add the "blinks").
I works ok when I klick on the sensor in test.tellmon.net in the normal way. In tellmon.net I still get the error.
Done, I got the database dumped on the screen, I think. No error (and no graph, just a screen full of data).
All sensors and graphs are working correctly. Even the "numerical" energy display (the one that show energy as degrees and the humidity counter) is updated correctly. It is only the energy graph that generates the fault code.
Yes, I still get it. The reading in columns "Last update" and "Data" are correctly updated, it's only when clicking on the graph symbol I get the error message. Once more, the graph as such was correct before I wrote the (unfortunate) ticket, sorry!