"Full Party" and "Light Party" effects cause lag

Occasionally (I'd say about 30% of the time) when I join a party, or when I'm in a party that becomes a full party, when the "Full Party" text pops up on the screen, it causes extreme amounts of lag to my client, to the point where the game becomes unplayable. Not only that, I've found that it actually slows down the rest of my running applications as well (for example if I alt-tab out into Chrome, as I play in windowed mode). The only fix that I've found so far is to fully exit the game and restart, which is very inconvenient, especially in Ifrit groups, etc. Another member of my linkshell also experiences the exact same issue, very frequently at the same time as me if we're in the same party.

I've also noticed recently that the same issue occurs during guildleves, at the end of the leve when the "white flash" appears signifying that you were victorious. Once again, it causes lag to the point where I must restart my game. If it helps, my PC hardware specs are as follows:

-Windows 7 64-bit
-Intel Core i7-960 Bloomfield @3.2 GHz
-nvidia GTX-480
-6 GB RAM
-speedtest:
http://www.speedtest.net/result/1588449236.png
-pingtest:
http://www.pingtest.net/result/50438801.png

Let me know if you require any other information.

Greetings, CSLionheart!
Thank you for posting your concerns about the latency that you have experienced. In order to make sure that we have sufficient information for a thorough investigation, it would be a great help to us if you could provide the names of the areas that you experienced this trouble in, as well as any coordinates. Also, any names of the guildleves that were involved that you can post would be appreciated. In addition, it may prove helpful to contact the the SQUARE ENIX Support Center about this matter. Thanks again for your participation!

To answer your question, I don't believe the glitch is specific to any area, guildleve or set of coordinates. I have noticed the glitch in numerous parties in numerous different areas, including Coerthas (outside Dzemael Darkhold), Ul'Dah, Thanalan (near the Ifrit aetherial node.) Also note that, once the glitch occurs, the lag will continue even if I enter an instance. For example, if we form a party outside the Bowl of Embers and then enter the instance, the lag will still remain even while inside the instance.

As for specific guildleves, I'm sorry but I can't name any from memory. Like I said, the glitch doesn't seem to be exclusive to any particular set of circumstances. The only pattern I've noticed is that it seems more likely to occur the longer I've been logged into the game. Also note that I have been experiencing this glitch for several months, since the launch of patch 1.18. Before 1.18, I had never experienced this problem. Hope that helps.

Greetings again, CSLionheart!
Thank you for providing the information that I requested. I have made sure to submit all of your information to the development team, and they will thoroughly investigate this matter, based on your report. Unfortunately, I cannot guarantee that a direct response will be posted on this thread, but I do recommend checking here or here for any details regarding the development team's investigation. Also, as mentioned in the previous post, I suggest contacting the SQUARE ENIX Support Center, just in case they may be able to help you find a solution to this situation. Thanks again for your report!