I'm also having similar issues. It seems that every 3rd or 4th patch rito F#&$ something up and this type of lag occurs.
Basically it's a 'rubberbanding' type of effect where some of the systems in the game seem to freeze or cease functioning, but not all. For instance, when the lag occurs, all minions and champions will appear frozen or will simply not appear at all (including jungle camps appearing to not spawn, even though I can see them on my minimap). However, during this time I can see my health bar going up or down and can click to cast spells or autoattacks (assuming the target is visible). This will occur for about 5 to 25 seconds and then afterwards, everything that occurred during that time span will suddenly 'rubberband' and quickly snap back to the way they should be in super speed.
This problem has occurred for me about 4 different patches out of the last 16 or so patches. This is chronic issue. Riot please fix this ASAP or at least let us know you are aware of it in the meantime. I've been playing and loving League for 4 years, but I am disheartened that these issues are still occurring with regularity.