The only reasons I can think of why that might not work are:

• visibility;

  When you try it from the Explorer, you've previously done a Tools->Map network drive, but you haven't done the equivalent before running the script.

• permissions;

  When you run the script, it is running under a different account -- say a webserver id -- that doesn't have permission to access the network.

What output do you see if you add the following to the top of your script:

warn `net share`;
warn `dir \\\\Server\\e\$`;
...
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