This may or may not be a bug...let's assume it's not for now...
This can occur sometimes when you queue a building or ship, then lose the labs necessary to perform that construction...you will need to rebuild the necessary labs to "reactivate" the technology...note that I think kostura shots and the Vasari shield ability (on civilian structures) disable structure functionality, so any labs affected by either of those things will not contribute towards prereq requirements until the buff affecting those structures times out....
Since you are VL, you also have the technologies that make your capital ships count as research labs...if you are depending on those and you lose them, this is equivalent to losing labs and you will encounter the same problem...
Another possibility for you is that you queued up the planetary infrastructure that increases logistic slots, then queued up the construction of structures...the structures cannot be built until the planetary infrastructure is finished....basically, the game knows you will have the slots, but you don't technically have them yet so constructors sit there and wait...