This story was updated on Friday morning with comment from Velti. 

Velti owes developers lots of money — and they’re looking to collect.

Just how bad is it? One in contact with collection agencies says Velti owes developers using Mobclix, its mobile ad exchange, an estimated $30 million, much of which these developers could end up attempting to collect via a class action lawsuit.

The developer, who has asked to remain anonymous because he’s still trying to collect payment, says Mobclix owes his company alone at least $500,000.

“Mobclix owes us pay from last October, and their last payment was in April,” the source said.

Mobclix, which Velti acquired in 2010, acts as the middleman between advertisers looking for ad space and the app publishers who are selling. While the platform has been prized for its higher-than-average cost-per-impression rates, those high rates are only enticing insofar as much as Mobclix actually pays them.

Many developers know this firsthand. Oliver König, the CEO of Germany-based app company Windfinder, told us yesterday he’s also still waiting on thousands of dollars in Mobclix payments.

“We first experienced delays last year,” König said in an e-mail to VentureBeat. “We contacted them, and they made their last payment on Feb. 6, 2013 for revenues generated until July 2012. They have not made any payments since then.”

Update: In a response emailed on Friday morning, Velti disputed the the $30 million number, which it calls ” completely inaccurate.” The company, however, says its unable to go into more detail because it’s preparing to report its second-quarter earnings this month.

“Velti values our developers. We are committed to paying outstanding amounts due to Mobclix developers and are working to do so as quickly as possible,” the company said.

It’s worth noting, however, that Velti’s contract with developers gives it 90 days to pay up — which gives it essentially a full quarter of wiggle room to pay.

What’s clear, though, is that investors are losing confidence in Velti’s approach. The company’s stock, which traded as high as $19.71 in the summer of 2011, has since plummeted to just $1.12 as of this report. Mobile advertising may only a part of Velti’s business, but it’s dragging the whole company down.

A hint of the situation can be seen in the company’s May 6K statement. In it, Velti reports $56.5 million in so-called accrued third-party costs — a large part of which refers to money it owes developers using the Mobclix ad network in their apps.

For the developers, the payment situation can go one of two ways: Either they can attempt to collect from Velti now (which could mean collecting only 50 cents on every dollar) or accept payments gradually over the next five years if Velti ends up restructuring. Either way, litigation seems certain.

The problem, however, is that Velti itself has some particularly severe cash flow issues, which is largely why it’s had such a tough time paying developers. As a middleman between advertisers and publishers, when Velti has issues collecting from one end, it inevitably has issues paying out to the other. This has been a significant issue for Velti over the past year.

Here’s Velti, again in its recent 6K, talking about its cash flow and financing problems:

While we anticipate generating positive operating cash flow for the year, this positive cash flow is not expected until the third quarter of 2013. As a result, we may need financing, in addition to the private placement recently completed, during the next three months to provide sufficient operational liquidity. This additional financing may be facilitated through the issuance of equity or debt.  If we need such additional financing, there can be no assurance that our efforts to find such financings will be successful, or on terms favorable to us.

The situation adds a bit of context to a May 13 e-mail that Velti business development director Mark Epes sent to one Mobclix developer:

Our payments have been a bit delayed due to some of the major demand partners having issues. These issues have all been put on payment plans and thus our payments to pubs are slowly getting caught up. To date we have always paid our developers every dime that they have earned. Some of these payments were and are late so I will not sugar coat the issue.

While situation is dicey, it is still fully possible for the company to pull out of it in one piece, said one hedge fund portfolio manager who asked to remain anonymous.

Velti could, for example, end up repairing its cash flow issues next quarter as promised, or it could raise more funds by issuing more stock. (The latter option hinges on the stockholder vote the company held yesterday, the results of which should come Monday.)

“None of this really spells the end for Velti. This is a normal thing for small companies that are growing,” said the manager, who has been following Velti closely. “Still, some companies never make it out the other side,” the person added.

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