This was just suggested for the exact same problem with my StreetPilot 2620 and worked like a charm:
(1) Disconnect any external GPS antenna.
(2) Do not turn on auto engine.
(3) Turn off any other peripheral devices.
(4) Simultaneusly hold down the PAGE and MENU buttons while turning on the 2620. A prompt box will appear asking if you really want to delete all user data. Touch the NO selection. Then turn off the 2620.
(5) Simultaneously hold down MENU & ROUTE buttons while turning on the 2620.
(6) A self-running diagnostic program will appear. Allow it to run for a couple of minutes; check to see that all parameters indicate "PASS" or other indication of being OK. If any parameter is not OK, make a note of it for potential communication to Garmin, then proceed with the following steps
(7) Turn off the 2620.
(8) Simultaneously hold down the PAGE, MENU & ROUTE buttons while turning on the 2620. A SCREEN CALIBRATION adjustment screen will apear. Quickly touch the points indicated as the calibration program runs. At the end of this procedure, the screen will display a window indicating that the calibration either "PASSED" or "FAILED." If it "PASSED," continue to steps (8)-(9). If it "FAILED," turn off the 2620 and repeat this step. If, after three calibrations attempts, each one is "FAILED," then also turn off the 2620 and proceed to steps (8)-(9).
(8) Turn on the 2620. Press the "OK" button each time prompted to do so. Wait for maps to load and for the 2620 to initialize, acquire satellites, and display your position.
(9) Press FIND button, then touch the right-hand vertical screen position adjustment to scroll screen display down to reveal WAYPOINT selection box. If unable to select WAYPOINT, or if attempting to do so only selects an adjacent box, then repeat step (7), and return to this step.
(10) When various waypoint selections appear, attempt to scroll down to a selection not visible when the list of waypoints first appears, and select one of them. If still unable to select WAYPOINT box, unable to scroll screen down (or if trying to do so selects a stored waypoint instead), once again repeat step (7). If successful,then proceed to step (11). Also proceed to step (11) if you have repeat step (7) but then still can't select WAYPOINT, can't scroll down after selecting WAYPOINT, or can't select a particular stored WAYPOINT.
(11) Press the upper-right hand "X" to close out the FIND screen or sub-screen within that function. If unable to close the screen, press the PAGE button.
(12) Press FIND button, and when selection screen appears, touch ADDRESS. On next screen, touch the STATE line and touch the ENTER A CITY in (name of state). When keyboard appears on screen, use it to enter your city, then touch OK. Continue this procedure to enter your house number and street name, then press "OK." If all screen keyboard keys not responding, repeat step (7), turn the 2620 off and on again, wait for it to initialize, and then attempt this step again.
(13) Repeat this procedure several times if not initially successful. By the second or third run-through, the touch screen should respond fully and accurately. If, after many runs through this procedure, the touch screen still will not respond, the screen sensor probably will need to be replaced ($255).
The foregoing procedure brought my touch screen back to life last evening, much to my delight. Do not be too concerned if the SCREEN CALIBRATION step does nto produce a "PASS;" on my third calibration attempt it produced a PASS but all of the touch screen points still had not returned to functionality. I was unable to get a PASS during the screen calibration step after that, but the many repetitions apparently nonetheless made the difference, as by patiently following the above prcoess for five cycles, full screen functionality was restored.
Thank you for rating this solution.
Good luck and save you $250 for something else!