I have temporarily another guruPlug, unmodified, so I used this other device to retrieve some files:
dd if=/dev/mtdblock1 of=uImage-GuruUnmodified
I'm in the same situation as you here and I've also managed to get my hands on a unadulterated plug to try and recover from.
I've run the command you mentioned above and I have couple of quick questions.
dd if=/dev/mtdblock1 of=uImage-GuruUnmodified
dd: reading `/dev/mtdblock1': Input/output error
1024+0 records in
1024+0 records out
524288 bytes (524 kB) copied, 0.771468 s, 680 kB/s
1) The file is only 512k which is a lot smaller than I was expecting (the other Kernel images where 2.6mb). How big was the file you managed to generate?
2) I take it I should install this (assuming it's the right size) via tftp like I did with the newer versions of the kernel that broke me earlier?
I've also tried reading from /dev/mtd1 and /dev/mtd1ro both of which give a 4mb file.
Thanks