Try 307 when it's out. It should give the coordinates of the bad cables in the client console.
That was quick! Thanks for the help. I could locate the cable that crashed the client and deleted it via MCEdit using my old 1.4.7 version (MCEdit just wipes everything mod related in the edited chunks).
And just to give you some help debuging the problem heres a screenshot of the cable:
http://i.imgur.com/QV22aS3.png
What you see here is a foamed diamond cable with a redstone torch on its side and redstone on top of it (all foamed cables crash the client). I hope that helps.
If you need any further informations just ask me, I always backup my worlds.
regards