Stuck/Freeze at Samsung Galaxy logo + using zImage built from source

[vasudeva.manjunath]

GalaxyTab details: GT-P1000 (European/Internation/Unbranded)

I have built "zImage" kernel image using Samsung opensource. (using GT-P1000_OpenSource_Update1.zip source).
zImage is built with initramfs.. (I have provided the INITRAMFS_SOURCE="/path/to/root")

I have rfs-based Stock ROM which is working fine.. (flashing/re-flashing)
I have rooted the Tab successfully using SuperOneClick
Used SGTBootloader patch which says

"Signed: Kernel
Not Signed: PBL, SBL, SBL_Backup
Assessment: Can flash anything"

The built-kernel is not signed.. Is it mandatory to sign the kernel?
How to debug the problem?
Any pointers will be highly appreciated..

Thanks and Best Regards,
- Vasu
P.S. I have successfully flashed Overcome 1.6.4 (both rfs-based stock ROM and ext4-based custom ROM) without any problem..