EDIT: Okay, I got the problem solved by FINISHING the soft reset procedure
https://wiki.mobileread.com/wiki/Sony_Portable_Reader#Soft_Reset
I'll leave my original post below to help other newbies in similar situations
*******
Sigh,
So, I just customized my 505 successfully with PRSC, and changed the font to one I liked using Valloric's excellent guide successfully. HAd to have a few goes to get both right, but everything worked fine
Then came the time when I was going to delete all the customization files off my memory card. I inserted the card into the reader, connected the 505 to my computer and realised I probably should be doing this the other way around, so removed the card before the computer could recognise it. Now my 505's screen is stuck on Valloric's "Run Scrpit" screen with the various options.
I've tried the reset button, and Valloric's guide to un-bricking the 505. Neither worked. When I run the "PRS-505 Updater.exe" it says my 505 isn't connected, though it is.
GAH! Please help