Delays in issuing virus updates were caused by security software giant Network Associates purchase of anti-virus software firm Dr Solomon's Group Plc. Users of Dr Solomon's Virex program were notified earlier this month that the September update for the software's virus definitions would be skipped. Thus, the users' systems could not be inoculated against any viruses brought to light in August. At fault: corporate restructuring. "With the integration of the software teams and a new version coming out, we have been a little delayed," said Sal Viveros, product marketing manager for Network Associates' Total Virus Defence group. Network Associates announced the $640m (£390m) acquisition in early June. Without the most recent update, Mac users will have to wait until next week, when Network Associates plans to release the next version, Virex 5.9. That version will have a new scanning engine and will be provided free to current users of Virex 5.8.1. "We did not create an upgrade because of the work on this new version," said Viveros. Users, however, were still not happy. Popular Mac site Macintouch posted a report citing several complaints from Virex users over the one-month hiatus in updating the virus definitions. Granted, the majority of users may not have even noticed the lack of an update. Updating anti-virus utilities is not at the top of most users' to-do lists, said virus expert Rob Rosenberger, who runs the Computer Virus Myths Homepage. "It's a big problem," he said in a recent interview. "People just don't update their virus software." However, a recent scare may change that. This week reports began circulating about a malicious program known as a Trojan horse that targeted Macs. Called "Graphics Accelerator," the program promises to speed up graphics on certain Macs, but instead actually causes some programs to display garbage and prevents others from running at all. While it doesn't accelerate graphics, the new program may cause even more complaints to pour into Network Associates.