Serious Spell Casting Issue with Elise (not a matter of FPS or server lag)

While playing a ranked game as Elise, both my abilities and summoner spells were not responding on time, if at all.

For example, while at point blank range fighting the raptor camp [in spider form], I was unable to cast my E, Q or smite. neither I nor my spiderlings were overlapping with the monsters, and there were NO FRAME DROPS OR LAG.

Example 2: While fighting the enemy brand with less than 200 health, i was unable to use any abilities - chilling smite, Human form spells and transform spells would not activate, despite all being off of cooldown.

NOTE: this issue has not occurred at any other time, in any other game today, with any other champion.