you might try running Solidworks Rx and cleaning out your temp folders
Another possibility is you've got a compatibility issue between SolidWorks and your virus scanner (you might exclude the SolidWorks process or file types from monitoring)
Another possibility is you've got a high-priority process that's interfering with solidWorks calls to the operating system-likely culprits are Raid 0 backup processes, turning on shadow copy in the BIOS and the indexing service.
You could also have a messy registry update from installing SW15. Try removing and re-installing SolidWorks if all else fails.