Saving source code

Suddenly after working on a file I get a message saying "Access is denied" & I cant save the source file. Everything was fine yesterday - dont dare shut the computer down as I haven't saved my alterations & the program is NOW doing what I want.

Arduino: 1.8.1 (Windows 7), Board: "Arduino/Genuino Uno"

Sketch uses 8922 bytes (27%) of program storage space. Maximum is 32256 bytes.
Global variables use 1004 bytes (49%) of dynamic memory, leaving 1044 bytes for local variables. Maximum is 2048 bytes.
java.io.IOException: Access is denied
at java.io.WinNTFileSystem.createFileExclusively(Native Method)
at java.io.File.createTempFile(File.java:2024)
at processing.app.BaseNoGui.saveFile(BaseNoGui.java:895)
at processing.app.SketchFile.save(SketchFile.java:287)
at processing.app.Sketch.save(Sketch.java:138)
at processing.app.SketchController.save(SketchController.java:344)
at processing.app.Editor.handleSave2(Editor.java:2044)
at processing.app.Editor.access$2100(Editor.java:77)
at processing.app.Editor$54.run(Editor.java:2029)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Access is denied

This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.

Maintann:
dont dare shut the computer down as I haven't saved my alterations & the program is NOW doing what I want.

Copy the contents of of the edit window(s). Paste the contents into a text editor (Notepad). Save the contents someplace safe.

at java.io.File.createTempFile(File.java:2024)

I suspect your anti-virus software needs to be replaced.

What operation are you doing when you get that error output? The start of the output is a successful compilation but I don't know whether that's just some output that was left over on the console.

Original sketch allows writing values to the lcd; this compiled, loaded & ran (& saved). Reopened days later to add additional routines to read & write these values to the eerom. Test compiled, fixed a couple of typos & uploaded the sketch successfully. Sketch ran as hoped but the IDE wont close & attempts to save the file get "Access is Denied" message.

So you're saying that the error message appears in the console when you do File > Save?