Gah...I lost my entire response because I tried to attach a batch file. Let's see...what did I type last time? hihi
I can program a nano from the Arduino IDE. Like you, I can no longer flash that nano with xloader. Crud.
Ok, plan B!
In the folder with xloader you should also see avrdude files. avrdude is a command line flash utility that works well even when xloader doesn't.
Here's a command string that works:
avrdude -C avrdude.conf -v -p atmega328p -c stk500 -P COM9 -b 57600 -D -U flash:w:UBITX_CEC_V1.100_16D.hex:iYou'll need to paste it into notepad (not wordpad or a regular word process as they include hidden characters), update the COM port number (mine's 9) and thename of the .hex file you want to upload, then save the batch file (load.bat, for example) into the same folder/directory as avrdude. when you edit the file name, make sure the flash:w: remains, as well as :i at the end. Leave the rest, including the 57600 baud rate.
With this batch file and the .hex file you want to load in the same folder as avrdude, open a command prompt. (Search for cmd.exe.) You may have to change to the drive letter your avrdude files are on. Mine are on I:. Yours might be on C: or D:. To change drives, enter the letter and colon, and press enter. Then change directories to the avrdude files. You can start typing and hit tab to auto-complete for long directory names. cd xloader<enter>. When you think you're in the correct directory, type dir to see a directory listing. When you know you're in the right place, type the name of your batch file (load.bat, for example) and watch the file transfer and be verified.