Is there a way to reset the JRun server from within a ColdFusion page?
Yep, you can restart any service you want. Just write a batch file and run with cfexecute.
<cfexecute name="#filepath#restartjrun.bat"></cfexecute>
In the batch file something like:
net stop "Macromedia JRun CFusion Server"
net start "Macromedia JRun CFusion Server"
As Ciaran mentioned though, it's always best to solve performance problems than rely of temporary fixes like this.