My understanding (and I'm happy to be proved wrong) is that the definition of insolvency is not that liabilities exceed assets but that the company is unable to meet its debts as they become due.
So for example a company that has a bank loan of 100k, trade debtors of 200k and assests of 150k has liabilities (300k) that exceed its assets (150k). However providing its cash flow allows it to continue to meet its debts as they become due then the Directors are not commtting an offence by continuing to trade.