It is erroneously stated that the Haunted Halls is a keep built into the cliffwall of the Starwater Gorge. The keep described is in fact Rivior's Keep, also known as the Killing Keep. 
DM's Sourcebook of the Realms, p40:
The news from Alturiak in the Year of the Prince (1357 DR) stating "Mellomir, sage of Arabel, claims to have discovered a great treasure in an old, abandoned dwarf-hold north of the village of Eveningstar" is referring to the Haunted Halls, the underground stronghold built for the bandit-lord Rivior by a group of clanless dwarves. [2, 3]
#2106 Forgotten Realms Adventures
The Zhentarim, p.125:
Maglor the Apothecary is described as having been a 1st-level halfling thief, which is highly suspect considering his son is a 5th-level human thief. 
#8442 Forgotten Realms Atlas
The Haunted Halls, p.142:
The keep described is not the Haunted Halls but Rivior's Keep, known to Evenors as the Killing Keep . This error likely came about as a result of an error in the Forgotten Realms Campaign Set, 1st Edition (see the errata for that product).
#9249 FRE3 Waterdeep
Map of Eveningstar:
Location 14 on the map is incorrectly described as Pillar Rock, which actually lies to the west across Redhand Pool and just to the northwest of the fields belonging to the House of the Morning. The location shown is the ruins of the old Thaddath farm. 
#9354 FRQ1 Haunted Halls of Eveningstar
Important Characters, p.6:
Maglor, the father of Maethlin the apothecary, is listed as a "NE hm T5, deceased". This text was transcribed incorrectly from Next Stop: Eveningstar in Dragon Magazine #157, which reads "Maethlin son of Maglor; Maethlin is the apothecary (NE hm T5) and secretly makes poisons." The earlier text from Dragon is correct. 
The author states that Emperel hopes to find the resting place of the Lords Who Sleep, destroy them, and loot their cave to prevent these evil men from rising and fulfilling a prophecy that they will sweep Cormyr into ruin. This is in serious disagreement with previous canon :
The Lords Who Sleep are great warriors who were placed into temporal stasis so that they would be available to protect Cormyr in its hour of greatest need.
Emperel and his ancestors are sworn to guard the Lords.
Alaundo's prophecy refers to "armies of the dead, and legions of devils."
In addition, the text from Cormyr contradicts itself. It is stated that Emperel wanders the Stonelands to prevent evil beings from finding the cave of the Lords Who Sleep, which is followed by the text that Emperel hopes to find and destroy the Lords. The latter text should be ignored.
The author erroneously states that the keep near the Haunted Halls are called the Haunted Hills. He is referring to Rivior's Keep, also called the Killing Keep. 
The text referring to the inns in Eveningstar "The top three are the Lonesome Tankard..." could give the wrong impression. There are only three inns in Eveningstar in total.
Local Militias, p.58:
The text referring to banners used by local militias "...half the town's own banner, divided per fess (vertically)." is in error. A vertical division of this type is properly called per pale.
#9545 Prayers from the Faithful
Leaves of Green, p.51:
It is stated that a caravan master found Leaves of Green floating in the ruins of Zhentil Keep after the latter was destroyed, which occured in 1368 DR . Someone bought the book from the caravan master in Arabel and was then devoured by predators in the Stonelands. A group of adventurers happened upon the corpse, which had lain there for a winter or more, and took the book to the House of the Morning in Eveningstar for identification. The adventurers retrieved the book and ventured into the Haunted Halls and were never seen again. In the paragraph following this information, it is stated that the most recent identification of the book was at an inn in Iriaebor in 1367 DR, which is two years prior to the earliest possible date that the book could have turned up there. There are two possible solutions to this quandry: 1. assume that the sighting in Iriaebor was false, or 2. make the date of the sighting there 1370 DR.
#11634 Into the Dragon's Lair
About Eveningstar, p.11:
Tessaril Winter is described as a Wiz12/Ftr8; she is now officially described as a Wiz12/Ftr6. 
About Eveningstar, p.11:
Charisbonde Belon is described as being female; Charisbonde was always previously described as being male and the 'Patriarch' of the House of the Morning in Eveningstar. [8, 9, 10]
Dragon Magazine Annual #5
The Steel Regent, p.63:
Alusair is described as a CG Ftr20; she is now officially described as a NG Ftr7/Rgr1/Prp2. 
Myrmeen Lhal, p.64:
Myrmeen is described as a CG Rgr13; she is now officially described as a NG Rgr12 with Tymora as her patron.