"Our priority is to resolve this issue as quickly as possible for our clients," it said.
However, Thomson Reuters' message to clients blamed "an issue at the exchange." The message is understood to have played a part in prompting the LSE to issue its own statement.
Interactive Data has not yet commented.
Netbuilder insisted it had carried out "all possible testing during the available testing time but there were some unforeseen issues encountered."
It said the price disappearance on its feeds on Tuesday morning was "no-one's fault." However, it added that it was owing to "a misinterpretation of the detailed technical specifications which resulted in a misunderstanding". This misunderstanding "wasn't fully uncovered in our test plans."
Netbuilder said it moved rapidly to make amendments to "some data processing logic" in order to correct the problem. It is understood several vendors experiencing problems have contacted the firm to ask how it solved the issue.
Monday's launch of the new matching engine, written in C++ language and running on Novell SUSE Linux-based data centers, was largely seen as a success in pure trading and matching stability terms, without any outages, in spite of the price data problems with some vendors and in spite of a closing auction delay.
The system replaced Microsoft .Net-based trading software that was written in C# by Accenture, and ran on Windows Server and SQL Server.
Compared to the eight-hour outage experienced during heavy trading in 2007 on the .Net system, TradElect, the price data problems are having a narrower impact, with most data firms correctly displaying prices. Nevertheless, with some of the largest data vendors still unable to provide correct pricing on certain stocks several days on, engineers continue to work into the night to tackle the problem.
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