I've been working on a drawing file for an extensive period and honestly don't know when I last saved. Recently I've been greeted with the error message "An unknown error occurred while accessing C:\PDM\....". Initially I thought it was relevant to disconnecting from the PDM whilst my computer slept. However, the error persists no matter where I chose the 'Save As' location.

Within the drawing I have several components drawn up for manufacturing, with different configurations (of same part) on different sheets. Its quite heavy with dimensions and seems to be getting a bit laggy but really wasn't expecting this. 

I found a thread in the old forum [Error while trying to save sheet format. | SOLIDWORKS Forums]. Which talks about a similar issue caused by pictures in the Sheet Format, but trying to save the sheet format itself. In this case I'm using our standard title block that has been in circulation for over a year, without issue. Although it does include a logo image. 

Currently if I try to edit the title block I am unable to select the logo.

Any help would be greatly appreciated, I've spent ages on this drawing and its imperative to get it out the door in the next few hours. Low-key freaking out!