<Solved> Bulb timer longer than 10 minutes

[Donald]

In M-mode I am able to use the 'bulb-timer' feature at a maximum of 10 minutes.

Unfortunately I am not able to make a picture with exposuretime 11 minutes or longer using 'bulb-timer'.
If I do make a picture of 11 minutes or longer:
The picture is made, but the image cannot be stored. The number of pictures I ought being able to store on the card begins to blink on th LCD screen after the shutter closes. It happens with both Jpeg and RAW.
I cannot make a new picture (camera busy appeares) without removing the battery.

Hope someone can tell what I should do... (or what settings I should change)

Canon 550D; Transcend UHC1 16Gb

[nanomad]

Do you have long exposure noise reduction on? That doubles the exposure time

[Donald]

Thnx! It was set as "automatic" It's function is new to me.