I'm going to preface with I'm doing this at work with my chain of command's blessing and may be beyond the scope of the forum, and I'll accept that as an answer. But I figured a few people may have had similar experiences or have an idea what's going on.
Earlier this week, I downloaded and installed v2.0.3 of the IDE on a Win 10 machine. It installed without a UAC prompt to my %APPDATA% folder and I didn't think too much of it. Launched it and it then asked for an Admin password and had my boss enter it into install the drivers and libraries it needed. Nothing weird to me so far.
I open an emailed zip containing my code (did it on a personal laptop at home) extract it to my arduino folder in My Documents. I open the code and it thinks for a few before opening a blank sketch_date. I try it again and it repeats the behavior. I can open the default sample sketches and those included by the libraries added (Onewire and Dallas Temp).
I open the from the zip without extracting it from the zip and the sketch opens up. I then copy the sketch to our T: drive and it opens from there.
For grins and giggles, thinking it's just a permissions issue, I run arduino as an admin and when I click the pinned my documents folder it opens the admin accounts "my documents" folder.
Like I said above, this is for work so as far as I'm concerned, it's not a burning issue. I have a work around by putting my code on a network drive.
Is there anything noteworthy about the path to the file at that location?
Folder Properties lists the location as \\$WORKNAME$\Users\utechtl otherwise I don't think there's anything too special.
What happens when you tried to open the sketch?
When double clicking the sketch from explorer with Arduino running as an admin, it still opens a blank file.
From Arduino's open file prompt clicking the pinned "My Documents" folder didn't open utechtl's "My Documents" it opened Admin's "My Documents". I didn't take too long with it running as admin, I was seeing documents that are way above my pay grade confidential. I'm not too sure I want to ask for the admin password to see what happens if i were to navigate to My My Documents folder as an admin.
What happens if you open it from a different location on the C: drive (e.g., C:\SomeArduinoSketch\SomeArduinoSketch.ino)?
Copying the folder to 'C:\Users\Lutecht.arduinoDE\SomeSketch' and opening the sketch works fine.
My unqualified thought is that something interesting is going on my when it accesses '\Addresses'
OOOH, hey, so i'm not too far off.
It appears that AduinoIDE doesn't like UNC addresses. You commented on another thread with a similar issue and specifically pointed out that it's in Eclipse.
OK, that is the problem, as you were able to discover yourself already (nice work!). Arduino IDE does not currently support opening sketches from UNC paths:
The workaround is to map the network share to a drive (if you haven't done it already), then open the sketch from the location under the drive instead of the network location.