Is Russian version correct? Russian TRF is the only file longer than Polish TRF.

If there is a problem with "Loading maps" you could try following trick:
While nuvi is booting press and hold power button. I'm not sure when is the right moment to press, maybe at Garmin logo or when first copyright text appear. If you get standard menu to turn nuvi off, select cancel and there is a chance, that nuvi will finish booting correctly. Then you can connect it to USB without turning it off and remove bad files.