I actually CAN get download mode (or what I assume it to be) running by pressing Vol- + Menu + Power (while Vol- + Home + Power wont do anything, nor does the USB jig that arrived today). Took me some time to discover this, as this doesnt seem to be the usual 3-button-combination used. BUT: while the phone is now recognized by my PC, it wont show anything on the screen.
Odin (tried 4.28 and 4.43 on both win7 x64 and x32 and everyting related to Kies shut down) does now detect my phone. However, it always gets stuck at "Setup Connection" when I try to flash the stock rom or CWMR. Tried different approaches (from starting DL-mode with the phone being connected to my PC to separately starting DL mode and then connecting, starting it up with the battery already being in place, starting it up with sliding the battery in place while holding the 3 buttons etc.), none of them gets me further so far.
Another hint I found was setting the Baud-rate of the Samsung mobile modem to 203400, but this, unfortunately, didnt change anything.
Anyone got a lead on how to get Odin finally started properly?