rom flashing - Fastboot erase system not working

My device: Karbonn A52+

Android 4.2.2

Mediatek MT6572 CPU

Root Access: Yes

Bootloader: Unlocked

I'm trying to flash the official system.img of my device's stock ROM which I have with me, over fastboot.

However, when I run the command: I get this...

C:\Users\Tanmay>fastboot erase system
******** Did you mean to fastboot format this partition?
erasing 'system'...

And this goes on forever. Does not go further this. If I directly run this command without going through the above process:

E:\OS\Mobile\adb>fastboot flash system system.img
erasing 'system'...

Same thing happens, it gets stuck at erasing 'system'...

Other fastboot commands work fine:

C:\Users\Tanmay>fastboot devices
mt6572v1_phone  fastboot

Also, commands like fastboot reboot, fastboot getvar all, work fine.

I'm only facing problem with erasing system. I am unable to figure out why it happens with this command. Is it possible I'm being impatient? I abort it if it doesn't respond after 3-4 minutes.