after reinstalling the whole system with the 0710 DVD for i386 I noticed, that my UIRT was receiving and learning the codes perfectly, but none of the codes were sent to the AV devices. This worked in 0704 perfectly.
When investigating the problem I noticed, that some other people had the same problem with the UIRT and the installed kernel 2.6.22. To make it short, the problem it within the ftdi_sio.c module, which is the (serial usb) driver for the UIRT. The problem didn't appear in 2.6.20 and is solved in 2.6.24, when comparing these two files and reading some more mailing lists and forums, I found a solution which works for LMCE 0710.
1.) Get the sources for your kernel
2.1) Edit /usr/src/[YOUR VERSION]/drivers/usb/serial/ftdi_sio.c
2.2) Find the function "ftdi_tiocmget". It should look like "ftdi_tiocmget(struct usb_serial_port *port, struct file *file)"
2.3) Within this function is a case-block, just after "case FT2232C:" add "case FT232RL:"
2.3) Save the file
3.) Rebuild the module by typing
cd /usr/src/[YOUR VERSION]/
sudo make drivers/usb/serial/ftdio_sio.ko
4.) Backup your existing ftdi_sio.ko module
cd /lib/modules/[YOUR VERSION]/kernel/drivers/usb/serial/
sudo cp ftdi_sio.ko ftdi_sio.ko.backup
sudo cp /usr/src/[YOUR VERSION]/drivers/usb/serial/ftdio_sio.ko ./
5.) Reboot your system
That's it, someone forgot a case statement and this caused all the headaches. Btw. simply changing the modules to an older version may work. However in my setup it didn't work, so I had to go the way described here.