Batch breaks after ebook-convert.exe

[j0s3f]

Hi,
just got my Kindle today and want calibre to send me news once a day.
The task should run on my Windows Home Server (basically a stripped down Windows 2003 Server)
I created the following three scripts:

kindle-send.cmd

calibre-smtp.exe -a %2 -s "%1" -r mydomain.com -u myuser -p mypass kindle-news@mydomain.com myusername@free.kindle.com "%1 News"

convert.cmd:

ebook-convert.exe %1 %2 --output-profile kindle

and finally send-news.cmd:

cd C:\Programme\Calibre2
del /F heise.mobi sueddeutsche.mobi standard.mobi
convert.cmd derStandard.recipe standard.mobi
kindle-send.cmd Standard standard.mobi
convert.cmd Süddeutsche.recipe sueddeutsche.mobi
kindle-send.cmd Süddeutsche sueddeutsche.mobi
convert.cmd heise.recipe heise.mobi
kindle-send.cmd Heise heise.mobi

Problem is, if I start the script it runs the first command of ebook-convert.com and then just breaks.
No error or anything.
The last lines of output are:

Serializing images...
MOBI output written to C:\Programme\Calibre2\standard.mobi
Ausgabe gespeichert in   C:\Programme\Calibre2\standard.mobi

C:\Programme\Calibre2>

It should obviously sent the standard.mobi via email and then start the next convert.

Very strange is, that if I start the send-news.cmd script in the same shell window again, it doesn't work.
No output...

C:\Programme\Calibre2>c:\Programme\Calibre2\send-news.cmd

C:\Programme\Calibre2>c:\Programme\Calibre2\send-news.cmd

C:\Programme\Calibre2>c:\Programme\Calibre2\send-news.cmd

C:\Programme\Calibre2>

Never seen anything like that before.
If I start a new shell window, I can start the script there, but it fails again after the first convert.
If I copy the commands one after one into a shell window, everything works fine!
Any idea what is wrong here?

[Manichean]

I think there was something about needing to call the calibre CLI commands with "start /wait command" because of the windows shell being stupid, broken or both.