Dear friends,
I attach one of the most wonderful documents I've ever seen.
Thank you very very much to the source.
I hadn't had the time yet to analyse this so big amount of data...
Wow thanks! I wonder if your source have a similar document for Baikonur launches?
For the likes of Johnathan and Ed, here are the stated reasons for Plesetsk R-7 launch failures (or at least from Google translation...

):
1. 1966-05-17 [Voskhod 11A57] (Zenit-4): Failure at T+ 96s due to a "gearbox" (?) failure of the D429-500 unit on block G.
2. 1967-06-20 [Voskhod 11A57] (Zenit-4): Block D's telemetry cable failed to separate at booster separation, causing it to collide with the core stage (block A) and rupturing its kerosene tank.
3. 1967-09-01 [Voskhod 11A57] (Zenit-2): Block I failure at T+295 seconds (something about a valve that did not close?)
4. 1968-01-16 [Voskhod 11A57] (Kosmos 199): Spacecraft failed to separate due to an electrical failure.
5a. 1969-01-06 [Vostok-2M 8A92M] (Meteor): Launch aborted 9.65 seconds after ignition command due to a rupture of valve "O" on block B.5. 1969-02-01 [Vostok-2M 8A92M] (Meteor): Second stage failure at T+ 258.4 seconds.
6a. 1970-02-26 [Vostok-2M 8A92M] (Meteor-1-3): Block A aft compartment caught fire before launch. Rocket rolled back to HIF.7. 1970-07-21 [Voskhod 11A57] (Zenit-4): Block A control failure at T+146 seconds due to on-board gyroscope cavity pressure drop (?).
8. 1971-03-05 [Voskhod 11A57] (Zenit-2M): On-board internal battery (model 21STSK-50) failure at T+120 seconds.
9. 1971-06-25 [Voskhod 11A57] (Zenit-2M): Failure at T+95 seconds after block B's thrust dropped for 93 seconds resulting from voltage drop of internal battery (model 21STSK-25).
10. 1971-12-03 [Voskhod 11A57] (Zenit-2M): Block A exploded at T+ 0.5 seconds due to foreign matter blocking the engine.
11. 1972-09-02 [Voskhod 11A57] (Zenit-4M): Failure at T+ 85 seconds due to block A's vernier support structure A7200-10 failing, causing 2 verniers to wildly oscillate.
12a. 1973-04-06 [Voskhod 11A57] (Kosmos 554): Launch aborted at preliminary ignition stage due to one valve of block A's engine not opening.13. 1973-07-04 [Voskhod 11A57] (Zenit-4M): Block A's programming tape recorder short-circuited in flight, leading to incorrect pitch setting.
14. 1974-05-23 [Soyuz-U 11A511U] (Yantar-2K): Failure at T+ 440 seconds due to block A not separating from block I (release lock A3120-0/8K75 failure).
15. 1974-08-30 [Voskhod 11A57] (Zenit-2M): Block A failure at T+249 seconds due to premature cutoff of hydrogen peroxide (product 0-30) supply.
16. 1976-07-01 [Molniya-M 8K78M] (Kosmos 837): Block ML upper stage failure left spacecraft in wrong orbit.
17. 1976-09-01 [Molniya-M 8K78M] (Kosmos 853): Block ML upper stage did not start due to failure of separating valve "O" (?).
18. 1976-10-04 [Soyuz-U 11A511U] (Zenit-4MKT): Block D prematurely separated at T+94 seconds due to connecting screw failure between block D and block A.
19a. 1978-11-03 [Soyuz-U 11A511U] (Zenit-4MKM): Block D engine started late due to control failure, led to abort at intermediate thrust level. 20. 1979-02-16 [Soyuz-U 11A511U] (Zenit-2M): Third stage controller failure (of electrical relay KD24) at T+290 seconds lead to engine valve "G" not opened completely.
21. 1979-10-12 [Soyuz-U 11A511U] (Zenit-6): Third stage lost thrust after oxygen tank pressurization system failure.
22. 1980-02-12 [Molniya-M 8K78M] (Kosmos 1164): Block BL's control moment gyroscope (model KI11-24-14) failed in flight, lead to incorrect orbit.
23a. 1980-03-18 [Vostok-2M 8A92M] (Tselina-D): Vehicle exploded on pad during hydrogen peroxide fueling, killing 48 people.24. 1980-04-18 [Molniya-M 8K78M] (Kosmos 1175): Fourth stage failed to ignite after oxygen valve 0657-OA failed.
25a. 1980-04-25 [Soyuz-U 11A511U] (Zenit-4MT): Launch aborted at 12.5 seconds (can someone translate the reasons?)26. 1981-09-11 [Molniya-M 8K78M] (Kosmos 1305): Fourth stage failed at T+3367 seconds due to engine explosion.
27. 1982-05-15 [Soyuz-U 11A511U] (Zenit-6): Block A shut down at T+28.26 seconds due to false shutdown command caused by the control circuit board contaminated with metal particles.
28. 1986-10-03 [Molniya-M 8K78M] (Kosmos 1783): Upper stage shutdown at T+3819 seconds due to a faulty transducer.
29. 1987-06-18 [Soyuz-U 11A511U] (Resurs-F1): Block D's oxygen turbopump exploded at T+6.31 seconds, probably due to foreign objects inside the pump.
30. 1988-07-27 [Soyuz-U 11A511U] (Resurs-F1): Control systems failure of the first stage at T+1.43 seconds. (Can someone help translate the details?)
31. 1990-04-03 [Soyuz-U 11A511U] (Yantar-4K2): Third stage failure at T+358 seconds due to control failure (?).
32. 1990-06-21 [Molniya-M 8K78M] (Kosmos 2084): Fourth stage pitch control failure due to power transformer short circuit.
33. 1990-07-03 [Soyuz-U 11A511U] (Yantar-4K2): Failure at T+123 seconds due to control system damage at booster staging, leading to loss of vernier control.
34. 1996-06-20 [Soyuz-U 11A511U] (Yantar-4K1): Payload fairing disintegrated at T+49 seconds, causing destruction of blocks B and D.
35. 2002-10-15 [Soyuz-U 11A511U] (Foton-M1): Block D pump explosion at T+20 seconds due to ingestion of foreign particles.
36. 2005-06-21 [Molniya-M 8K78M] (Molniya-3K): Block A failure at T+298.6 seconds due to valve leaking for 26 seconds caused by oscillations.
37. 2011-12-23 [Soyuz-2-1b 14A14B] (Meridian 5): Third stage failure at T+421 seconds due to helium pressurization system leakage.