Despite positive gains for its IP services, XO Holdings posted a slightly higher net loss for the second-quarter this week and saw a dip in revenue over the same period.

XO, which operates Nextlink Wireless and XO Communications, posted a net loss of $36.8 million in the second quarter compared to $36.1 million for the same period last year. It also reported revenue of $352.9 million, down from $354.3 million in Q2 2006.

The company did see growth in data and IP services revenue, which netted $125.7 million in the second quarter, up 18% from Q2 2006. Revenue from XOptions Flex, the company’s flagship business voice-over-IP service, grew 131% to $18 million during the quarter and passed the 10,000-customer mark.

“Overall sales performance in the second quarter was our best in two years, and our strategic network, customer and service initiatives are delivering improved margins and revenue growth in IP-based services for enterprises and wholesale services for carriers and service providers,” said Carl Grivner, CEO of XO.

XO recently announced an expansion to 37 markets. The company also signed an agreement with Hatteras Networks for deployment of Ethernet-over-copper technology in 60 major metropolitan markets.