Recover possible corrupted SD card?

[aquarius18]

I hope I posted this in the right forum - if not, please forgive me.

I am running XBIAN Alpha 3

All worked absolutely fine until this morning. My Pi has been running constantly, never turned it off. No changes made to overclocking, runs on XBIAN speed (I believe that's 840 MHz).

This morning tried to ssh into Pi to check if any updates were available. Got "no route to host", so checked "Attached Devices" in my router. Sure enough: the Pi failed to show up.

Tried to reboot by physically disconnecting and reconnecting the power plug (something I would never do under normal circumstances!!)

The boot screen shows the usual processes until it gets to this:

(the following had to be written down on a piece of paper first so some stuff is incomplete...)

EXT4_fs (blah blah..)
ext4_check_descriptors: Checksum for Group 15 failed (.. blah....)
EXT4_fs (blah blah..)
group descriptors corrupted!

... blah blah

No file system could mount root, tried ext4
Kernel panic - not syncing:VFS:unable to mount root fs

..... another 4 or 5 lines of numbers and letters - then the booting process stalls

+ + +

Firstly I checked if the PI itself had a hardware problem. Inserted another SD card with the stock Raspbian OS. Boots just fine, runs normal so convinced that the PI itself is healthy.

The SD card I am using is an AMICR 8GB Class 10 SDHC which has been working just fine for almost 3 months.

I am not a complete Linux novice, all my other machines are running various Linux distros, so I have a fair understanding of the whole boot process.... still - I am lost what to do now!

Can anyone give me a hint on how to try and recover this install please?

Thanks / Frank