During the early days of the Iraq invasion, some Marines were forced to use as many as seven different radios to communicate with colleagues and superiors. That's why the Defense Department has been working so feverishly on "Jitters," or JTRS, the $5 billion Joint Tactical Radio System effort to replace 750,000 old-school radios with software-based models.

But now, National Defense magazine reports, Jitters may be in trouble.

Encryption problems and an array of other technical shortcomings are throwing the entire project into question, said industry sources...

The JTRS version known as “cluster 1,” intended for use aboard Army helicopters and ground vehicles, is scheduled for a major Defense Department review this summer.

An Army technical review, known as “early operational assessment,” is slated for April. In January, however, the Army ordered the contractors to halt JTRS-related work for at least six weeks.

“Technical challenges were encountered during development and integration that indicated the need for upgrades in performance and modifications in design,” said Timothy Rider, spokesman for the Army Communications and Electronics Command.

This marks a sharp reversal of fortune for JTRS, which was hailed by Pentagon officials in 2002 as a “transformational” program that would underpin the Defense Department’s vision of an interconnected “network-centric” military force...

The Army declined to elaborate on what exactly the technical issues are that potentially could derail this program. Industry sources contacted by National Defense indicated that one key area of concern is the encryption technology, which is overseen by the National Security Agency. Changes in the JTRS “security architecture” requested by the NSA potentially could delay the deliveries of JTRS cluster 1 by two years. Unlike previous generations of military radios, JTRS is entirely software-based, making the system more susceptible to hacking and prompting NSA to tighten the encryption requirements.

THERE'S MORE: NSA concerns aren't the only reason Jitters is being delayed, Inside Defense notes.

The system’s processing and memory capacity included no room for growth. Studies showed that the limit of the system’s random access memory was likely to be exceeded and would lead to “possible erratic performance that would be difficult to isolate,” said Tim Rider, a spokesman for the Army's the Communications-Electronics Life Cycle Management Command.

As a result, program officials determined that moving from the prototype’s early limited functionality to the final design “would not be possible,” Rider said...

Program officials realized the challenges would lead to cost increases by October 2004, Rider wrote in response to questions. There were three key signs. First, Boeing needed more resources to finish hardware and non-waveform software requirements that would address memory shortfalls. Next, new baseline requirements emerged. Also, evolving operational scenarios and the development of the Defense Department’s Global Information Grid expanded the understanding of a networked system of systems, which has driven upgrades to the radio system architecture that are needed to comply with National Security Agency standards...

In January 2004, the program received a reserve fund of $159 million for potential financial risks that were known to exist before the contract award. Boeing and the Army program office are preparing a plan and cost estimate for any additional cost increases and cannot provide specific figures until that process is complete, Rider said.