Hi golfbananajam. Thank you for your help. The wireless mice are both rechargeable while the wired ones are powered from the PC. They all give the problem and it happens on single clicking. The rechargeable ones fail whether they be fully charged or not.
Hi spitoon. It certainly does seem to be more likely to go wrong when I am changing applications. I'll bear your other ideas in mind but will follow up on green granite's one about asking the MS forum for help first.
Thanks for that suggestion, green granite. I have just posted it on the MS forum so will now wait to see if there is any response.....