I agree with 4-2ndtwin. Don't give up, and follow his suggestion.
In fact proceed according to the following sequence. If Step 1 solves the issue, stop there, otherwise proceed to step 2, and then if necessary step 3.
Step 1) 4-2ndtwin's suggestion. Download "I777UCKH7-CL503881 FULL tar.md5" from the section titled I777UCKH7-CL503881 Stock Binaries. Flash with Odin3 v1.85 (preferred version). Perform wipe data/factory reset from within recovery.
Step 2) Download the Tar version of Siyah 2.6.14 Kernel. Flash it in PDA. Without ticking Re-Partitioning. Next repeat Step 1 above.
Step 3) Download the SBL Bootloader from the Download Repository. Flash it as PDA in ODIN, without ticking Re-Partitioning. (Please observe normal bootloader flashing caution.) Next repeat Step 2 above.
To recap the above for clarity:
Step 1 - I777UCKH7 full distribution --> wipe data/factory reset
Step 2 - SiyahKernel v2.6.14 --> I777UCKH7 full distribution --> wipe data/factory reset
Step 3 - Secondary Bootloader --> SiyahKernel v2.6.14 --> I777UCKH7 full distribution --> wipe data/factory reset