Have just upgraded my 2860 router to this new release firmware and whilst it is working fine I cannot get back onto the GUI, it returns the following error.

File System Invalid.

The file system of Web-based UI is inconsistent with router's firmware.
Please check the firmware version.

Is this a known issue, how can it be resolved, does this mean I need to roll back to an older version and how can this be done with no working GUI?

it seems you have tried a non compatable firmware, perhaps clicked wrong tab (from another model) when downloaded the firmware
For the 2860 go here
http://www.draytek.co.uk/support/downloads
Assuming you still able to access the WUI interface, if not reboot the modem & try again

The right firmware was used, I have a 2860N+ and used that download from the site (still have the file I downloaded with the v2860_378.all firmware file on my machine) So this new firmware looks like it has bricked my router, it is working but I now cannot access the GUI at all, I cannot see a way to up/downgrade the firmware from the CLI either, the unit is still in warranty so I'd be looking to have this replaced under warranty as its the official firmware that's caused the issue.

You can try reset the unit by holding the reset button (at front) with a small pen for 4-5 seconds (all settings will be lost)

If now you have access to the normal menu (192.168.1.1) go at System Maintenance >> Firmware Upgrade and use the *RST* file extension & update one more time t the latest firmware, will not harm the unit, perhaps is better

The *rst* file will set back everything to factory default (all settings) and a manual setup of the settings is the best option
You can leave it as it (just with master reset & reconfigure everything from the begin) or you can load one more time the firmware with the *rst* file extension

The *rst* is recommended after a major firmware update (example 3.3.7.1 to 3.7.8) for a fresh installation
This is because it helps avoid conflict with the newer added features or conflict with previous older settings

If still you don't have access to the System Maintenance >> Firmware Upgrade after a reset (which you can not update again the firmware with the *rst* file extension) ... & if the unit is not back on the way to the shop ... come back to guide you how to perform a reflash with the firmware utility tool

I too have the 2860N+ and upgraded to 3.7.8 with the correct download and have a partial GUI interface with only the Auto Logout list box visible!!

BomereShrew wrote: I too have the 2860N+ and upgraded to 3.7.8 with the correct download and have a partial GUI interface with only the Auto Logout list box visible!!

If not appeared other option apart autologout could be bug ... the *rst* file is best option over a firmware update but will return everything back to factory defaults, if there are too many settings then i know is difficult so try a previous backup
You can go to System Maintenance >> Management & tick Default:Disable Auto-Logout if it suits your needs