I had what looks to be the exact same error for about a month. I finally was able to fix it this afternoon. This is what worked for me, and this may or may not work for you.
First, go to the A:\Program Files (x86)\.technic\assets\objects directory. If there is a folder named "cd" then your issue is not the same as mine. If you cannot see a folder named "cd" then attempt to make a new folder and name it "cd". One of two things will happen. Either the folder will disappear, or windows will pop up an error window that says something of the nature of "Error 0x80070103: There is no more data available."
Assuming either of those happen, there may be a filesystem filter in place that is blocking your and the launcher's access to folders named "cd". You will want to open a command window and enter the command "fltmc filters". This will show a list of all filesystem filters that are active. In my case, there was a filter with some garbage name. I used "fltmc unload <insert_filter_name>" to remove the filter.
After that, the folders named "cd" suddenly became available and Technic Launcher was able to download packs again. Please let me know if this works for you.
