[Samsung Galaxy R i9103] 1337SereniTyx3:
First of all, you should carry out these steps in order to make sure if your cell is UBS Bricked or not:-

1) Try reinstalling Kies.

2) GOOGLE DRIVERS for your phone.

3) Try connecting via another pc usb port.

4) Try on different PCs or format the current one and try again.

5) Try using different usb cables and wall chargers to check whether its detecting and charging or not.

6) Mobile Odin[Not yet compatible with our device though. Chainfire is working on it.]

7) Clean your phone's mini USB port with the help of a toothbrush or a toothpick or blown air.

8) Use USB Jig [I WON'T RECOMMEND IT AS IT IS TOO DANGEROUS AND CAN HARM YOUR MOBILE]

11)Try toggling Bluetooth and then connect to PC. Check if that works.

12)Having the phone connected to PC and then turn on the PC.

IF THE ABOVE STEPS STILL DOESN'T WORK, READ BELOW

My case:-

-Rooted

-CWM Recovery Installed.

-Download mode accessible.

-Won't detect on any PC or laptop or any other. Even Odin won't detect it. Same when phone is in download mode. [Kies reinstalled & updated. Google drivers for our phone installed]

-Won't charge via a wall charger or USB cable either.

-Won't charge even when turned off and wall charger connected to it. Only the charging logo keeps flashing. But doesn't really charge.

-Won't charge even after wiping cache, dalvik cache & battery stats.

-Won't charge even after flashing different kernels via CWM. Nor does it charge after flashing stock kernel.

-Won't charge after flashing different ROMs

*Charges when connected to PC continuously for the third time.

NOW DO FOLLOWING STEPS TO GET BACK ON STOCK ROM, UNROOT IT AND GET BACK ON STOCK RECOVERY SO THAT YOU CAN GET IT REPAIRED WITHOUT VOIDING YOUR WARRANTY.

**IMPORTANT:- Make backup of your /efs folder using any Root Explorer before doing anything below. Keep that backup on your SD card. In case your IMEI gets messed up, it is the only way to recover it.**

1) First of all, make sure you do have a CWM backup of your country's stock ROM with no root. If you don't have it, tell your friend to do it. Then get that backup on your SD card so that you can restore it.

[Worked in my case. But I'm not sure if it also restores /efs from your friend's cell. If it does, your IMEI might get changed. DO IT ON YOUR OWN RISK].

2) If you've done the step above, start from here. First, factory reset on the current ROM you're on. Let it reboot. Now shut it down again and reboot into CWM recovery. Wipe cache, dalvik cache & battery stats.

3) Restore the CWM backup of your country's stock unrooted ROM which I've told you in the first step. To do that, go in CWM recovery-->Backup/Restore-->Restore-->Select your file-->Select YES.

4) After restoring is complete, let it boot successfully. After it gets settled, again factory reset. Again Wipe cache, dalvik cache & battery stats. Reboot.

5) Let it reboot completely. NOW TO UNROOT your cell, remove apps that you pushed to /system/apps (and superuser at the end) with root explorer and do a factory reset. Let it reboot. Download Root Checker from Market and check the status. If it says "Not Rooted", then congratulations! You've successfully unrooted your cell.

[Or just flash "unroot.zip". Now repeat Step No.2 again.]

6) Now again repeat step 3. After restoration, again factory reset and let it reboot.

7) Now to go back to stock recovery, download the file I've attached in this thread and put it in your SD card. Reboot into CWM recovery. Install zip from sdcard-->external_sd-->stock_recovery.zip-->YES.

8) Let it reboot. Again switch off the cell and go to recovery. Check if it takes you to Stock Recovery. If yes, then you've successfully got back on stock recovery! :)

Now you can give your cell to repair without the fear of voiding your warranty and save your ass from paying the expensive repair cost! :P :D

(*I'm not responsible for any harm caused to your mobile as there is risk in every ROM,Kernel,Mod etc. you flash on your cell.*)

You might wanna check out the fixes below but I won't recommend them because they are not safe at all. Do it on your risk:-

http://xdaforums.com/showthread.php?t=1120880&highlight=usb+brick

In case you mess up with your IMEI:-

http://androidadvices.com/recover-imei-samsung-galaxy-s2-android-phone/