I haven't dealt with this problem yet but you may me able to clean your cache of a script that your mshta is running.
Try running these commands in the Run box:
SFC/PURGECACHE
SFC/SCANNOW
If that didn't work
I would attempt to repair the installation - you should seek professional assistance before doing anything that may jeopardize your data.
But maybe one of the other GFYers know more about this.
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