Number Generator Duplicate

I am having a problem with the sequential number generator inside of Enterprise PDM 2009.  We are using the generator to pull numbers for our ECN forms (engineering change notices). Each number follows the same format (ex: 0123-09) the 09 is for the year and the 123 is supposed to be pulled sequentially next would be 124, 125 etc. We use the template manager to create an individual folder, rename the document to the ECN # and place it in it own folder.  The problem we are having is every once in a while the number generator will duplicatea number that has already been used. Since we have must use unique names inside of our vault the generator will change the -09 to -092.  This will only happen once and then it will continue on in the correct order.  Could this be a connection error for the user?

Thanks

SolidworksSolidworks Pdm enterprise Pdm