Thomson Reuters' currency trading platform was hit by intermittent outages yesterday morning.
Dow Jones, citing traders, says Australian and New Zealand dollars and sterling was affected by the problem, which began at around 06.50 GMT.
Risk Magazine says Thomson Reuters Matching was out of action for four hours, affecting liquidity, although the issue hit at a quiet time for the market.
Banks' own systems are unaffected and the rival Icap-owned EBS platform has seen an increase in activity as it picks up the slack, a spokeswoman told Dow Jones.
In a brief statement, the firm says: "Thomson Reuters Matching customers globally experienced service disruption yesterday but the service was restored and is fully operational."
Reuters Experiencing Currency Trading Outages-Traders - Dow Jones