Party members invisible/untargetable in Praetorium boss fights

[Aethlin]

Date & Time:
first occurence for me was on 22-09-2013, around 7:25pm (GMT+2) (but it has occured every time I entered the "Praetorium", in varying degrees of severity)

Frequency:
Always

Character Name:
Aethlin Minithar

Race:
Lalafell F

World:
Duty Finder (entered from Leviathan)

Class/Level:
WHM/50

Area:
Praetorium, Research Level, Laboratorium Primum and The Echelon

Party or Solo:
Party, 8-man
(though solo Duty Finder queue)

NPC Name:
None

Monster Name:
Nero Tol Scaeva, Gaius van Baelsar

In-Game Time:
varies

Steps:
1. I entered the dungeon “Praetorium” alone through the Duty Finder and was partied with others.
2. My party and me were following the dungeon objectives normally.
3. The first time in the “Praetorium” both me and my party members watched the cutscenes. In the subsequent runs I skipped them, as did most of my party members.
4. After the cutscene that plays right before the battle with Nero Tol Scaeva, a number of party members had disappeared.
5. After asking where they had gone, we discovered that while the minimap and their own chat messages placed them right around me, I could not see or target them. The amount of party members, and which one(s) would become invisible/untargetable, changes every time I enter the “Praetorium”.
6. The stats of the missing party members show up normally in the Party window, but they can’t be targeted, similar to when a party member is far out of range in a normal situation.
7. Even though I can't see or target them, the missing party members can still see, and target, me. Usually, for them everything seems as it should be. One time, the other WHM in the party had the same problem as me, although for her only one party member had disappeared (a Paladin tank), while for me, in addition to the same tank, a Monk was also ‘missing’.
8. The missing party members will still take damage and get targetted by enemies.
9. Medica, Medica II and other untargeted and/or party-wide skills still affect the ‘missing’ party members normally.
10. I can still target all enemies and visible party members normally.
10. During the fight against Nero Tol Scaeva, the purple beam that links a Magitek Death Claw to a player is aimed (diagonally) down and disappears beneath the floor when a ‘missing’ party member is targeted.
11. After the cutscene that triggers on entering The Echelon after the fight against Nero Tol Scaeva the same party members remain invisible/untargetable.
12. After the cutscene before the fight against the Ultima Weapon all party members are visible and targetable again.

note:
I made a screenshot during the first of my "Praetorium" runs, though it is not that clear since it's what I'm not seeing that is the problem. On this screenshot, the Paladin and Marauder were standing right next to Nero, the Monk and the Dragoon (at least on everyone else's screens XD), however they don't show up for me. Neither do the Black Mage and White Mage who where supposedly standing right next to me and the Summoner.
http://oi39.tinypic.com/2usel4x.jpg

Connection Specs
(as best as I can discover, my landlord has the precise specifications, but he is unavalaible at this time)

ISP:
Ziggo

Type of Internet Connection:
should be DSL

Internet Connection Speed:
at least 1Mbit/s

Modem maker/model number:
Sitecom (Wireless Network Broadband Router 54G)

PC specs

Laptop Model/Number:
HP EliteBook 8540w
------------------
System Information
------------------
Time of this report: 9/27/2013, 12:20:05
Machine name: BIG-ONE-HP
Operating System: Windows 7 Professional 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_gdr.130801-1533)
Language: Dutch (Regional Setting: Dutch)
System Manufacturer: Hewlett-Packard
System Model: HP EliteBook 8540w
BIOS: Default System BIOS
Processor: Intel(R) Core(TM) i7 CPU Q 740 @ 1.73GHz (8 CPUs), ~1.7GHz
Memory: 8192MB RAM
Available OS Memory: 8120MB RAM
Page File: 9635MB used, 6601MB available
Windows Dir: C:\windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: 96 DPI (100 percent)
System DPI Setting: 120 DPI (125 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7601.17514 32bit Unicode
---------------
Display Devices
---------------
Card name: NVIDIA Quadro FX 1800M
Manufacturer: NVIDIA
Chip type: Quadro FX 1800M
DAC type: Integrated RAMDAC
Device Key: Enum\PCI\VEN_10DE&DEV_0CBC&SUBSYS_1521103C&REV_A2
Display Memory: 4095 MB
Dedicated Memory: 978 MB
Shared Memory: 3117 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
Monitor Name: Algemeen PnP-beeldscherm
Monitor Model: unknown
Monitor Id: LGD0220
Native Mode: 1920 x 1080(p) (60.020Hz)
Output Type: Internal
Driver Name: nvd3dumx.dll,nvwgf2umx.dll,nvwgf2umx.dll,nvd3dum,nvwgf2um,nvwgf2um
Driver File Version: 8.17.0012.9688 (English)
Driver Version: 8.17.12.9688
DDI Version: 10.1
Driver Model: WDDM 1.1
Driver Attributes: Final Retail

[Xetyline]

Greetings Aethlin!

Thank you for posting your concerns with targeting inside the Praetorium. 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. Thanks again for your report!

Regards,
Xetyline