Much to my embarrassment, I managed to brick my nüvi 1490T. Here's what happened:

I was busy creating backups of the NV of my GPS units as per instructions here: [Only registered and activated users can see links. ]
Started with several nüvi 2x5W units. Experienced no problems. Then moved on to my nüvi 1490T. I changed the folder name X:\Garmin\Updater\0827 (for nüvi 2x5) into X:\Garmin\Updater\0972 (for nüvi 1490), got distracted, put the microSD in the unit and switched it on. Only after noticing the unit got bricked, I realised I had stupidly forgotten to change the *.bin file. It was still the one for the nüvi 2x5! When I now switch on the nüvi 1490T, it briefly flashes the message SYSTEM SOFTWARE MISSING.

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I can get into pre-boot mode, but trying to flash cure FW with GarminCure3 and Updater.exe results in an error message, saying "No updates available for your product" (Updater.exe recognizes the unit as a nüvi 2 series, not as a nüvi 1490).

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Then converted the original nuvi13xxand14xxseries_GCDFile__620.gcd file into a "out.rgn" file with RGN Tool v0.78 and tried flashing that into the unit using Updater.exe. First of all, as mentioned, Updater sees the unit as a nüvi 2 series. Then it appears to be updating, but finally shows an error. See screen shots below of the sequence of events.

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As per checklist here: [Only registered and activated users can see links. ] please find the answers below:

1. nüvi 1490T, intended FW 6.20 but suspect now FW 7.60 for nüvi 2 series, intended HWID 0972 but now suspect 0827 for nüvi 2x5W.
2. See information above how it got bricked.
3. See information above for symptoms.
4. The PC does not see the GPS as a mass storage device (message SYSTEM SOFTWARE MISSING keeps flashing on the GPS screen).
5. See information above for all attempts made.
6. Yes, Garmin USB drivers are installed on the PC.
7. Original HWID = 0972.
8. Yes, tried GarminCure3.
9. Yes, I can get into pre-boot mode.
10. No, I do not have a NV backup (was actually trying to create one when this happened!).
11. For what it's worth... I do have another nüvi 1490T (which works).