Just filtered the CONFLICT entries from my tekkit server log:
CONFLICT @ -49 item slot already occupied by dan200.computer.shared.ItemComputer@1fff293 while adding net.minecraft.server.ItemBlock@8e91eb
CONFLICT @ -48 item slot already occupied by dan200.computer.shared.ItemPeripheral@df8f81 while adding net.minecraft.server.ItemBlock@1467c59
CONFLICT @ -37 item slot already occupied by ic2.platform.ItemBlockCommon@783df while adding net.minecraft.server.ItemBlock@162c756
CONFLICT @ -30 item slot already occupied by ic2.platform.ItemBlockCommon@d1e63 while adding net.minecraft.server.ItemBlock@145fed7
CONFLICT @ -17 item slot already occupied by ic2.platform.ItemBlockCommon@165e7a5 while adding net.minecraft.server.ItemBlock@14b3397
CONFLICT @ -19 item slot already occupied by ic2.platform.ItemBlockCommon@283482 while adding net.minecraft.server.ItemBlock@18f67d0
CONFLICT @ -20 item slot already occupied by ic2.platform.ItemBlockCommon@1e8ad64 while adding net.minecraft.server.ItemBlock@cf8c7f
CONFLICT @ -18 item slot already occupied by ic2.platform.ItemBlockCommon@10fcd4 while adding net.minecraft.server.ItemBlock@146fac0
CONFLICT @ -78 item slot already occupied by net.minecraft.server.ItemBlock@86fe3a while adding codechicken.enderstorage.ItemEnderChest@9cd2bb
CONFLICT @ -204 item slot already occupied by net.minecraft.server.ItemWithAuxData@b6e2fe while adding net.minecraft.server.ItemMobSpawner@f0be2c
CONFLICT @ -40 item slot already occupied by dan200.turtle.shared.ItemTurtle@718b01 while adding net.minecraft.server.ItemBlock@5d0fb4
Looks like those are the same items Your log shows. A quick look through a ID-Map-Dump made on the client reveals that those blocks are: Log, Leaves, Sponge, Glass, Web, Flower, Mushroom, Mossy Stone and Obsidian. I spawned all of those blocks on my Tekkit server and they seem to work flawlessly although i cant say why those errors get spammed upon start. Tekkit team, got any ideas ?