I've tried with both Chrome and IE 9. Both give the same error: Error code: 18001 Upgrade unsuccessfully because the length of the upgraded file is incorrect. Please check the file name.

Matthew cook wrote Before you upgrade the router, did you unzip the file that was downloaded from web? And did you download the correct firmware for V4? Actually I didn't unzip it initially, until...

Similar issue here, though I'm starting from a different firmware version: I have: Firmware Version: 3.13.12 Build 120601 Rel.62521n Hardware Version: WR741ND v4 00000000 Trying to upgrade to the...