Venture capitalist Davidi Gilo had given up on the $6.5 million his firm invested in the enterprise software company BackFlip, which shut down in early 2011. But seven months later, he alleged in a lawsuit, he discovered that BackFlip’s software and customers had been subsumed by Cisco Systems, with the help of BackFlip’s co-founder, Gil Perez. And Mr. Perez had taken a job with Cisco.

“They bought the company. They just forgot to pay for it,” Mr. Gilo said in an interview. Through BackFlip, which still exists as a legal entity, Gilo Ventures has sued Cisco for breach of contract and theft of trade secrets.