I noticed it yesterday but was able to properly look at it today. When I use my Hemoplague ability (while playing Vladimir obviously) and put it on the ground, I can't use any of other my spells for a short time afterwards. It lasts about a second and all commands besides movement, auto-attack commands and summoner spells seem to be ignored. It is really, really annoying because this was never an issue before the patch and the sudden lack of an action has killed me several times already.
And since I tried it out on Dominion, it should also be said that when I Hemoplague and try to capture a point, the spell won't cast until a second has passed, proving that the invisible lock out of abilities includes the hidden capture spell.
Please fix this! It is so painful to lose the fluid motion of my favourite champ.
EDIT: Further information. The bug has occurred on both Crystal Scar and Summoner's Rift (Normal, Ranked, Custom and Co-op vs A.I), it is irrelevent what the Hemoplague hits (Neutral, minions, champions, mixed, nothing) as it always triggers a 1 second period where spell casts do not go off at all. The bug also affects all three ranks of Hemoplague.
I can still attempt to give the command but nothing happens when I am in range however if I am not in range to use Transfusion, Vlad still runs to try to be in range and if it takes longer then a second to reach the target, Transfusion will go off normally. The second delay is still there for moves I can't target with however. (Sanguine Pool, Tides of Blood)
Summoner Spells (Ghost, Ignite and Flash at least, I have not tested others) work normally in all cases.
I only call it a silence but it doesn't actually prevent me from trying to cast the abilities, they just don't go off unless it takes a second to reach them as mentioned above.
As of March 6th this is STILL BUGGED!