I wouldn't blame it on Seamonkey
sniped of your dmesg
there is a known Kernel bug[74970.320292] usb 2-1: reset high-speed USB device number 2 using ehci-pci
[74970.484464] sd 6:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[74970.484468] sd 6:0:0:0: [sda] tag#0 Sense Key : Unit Attention [current]
[74970.484471] sd 6:0:0:0: [sda] tag#0 Add. Sense: Not ready to ready change, medium may have changed
[74970.484474] sd 6:0:0:0: [sda] tag#0 CDB: Write(10) 2a 00 00 30 13 58 00 00 08 00
[74970.484477] print_req_error: I/O error, dev sda, sector 3150680
[74970.484481] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 393836)
[74970.484484] Buffer I/O error on device sda3, logical block 262763
[74970.484747] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 393845)
[74970.484748] Buffer I/O error on device sda3, logical block 262768
[74970.484750] Buffer I/O error on device sda3, logical block 262769
[74970.484751] Buffer I/O error on device sda3, logical block 262770
[74970.484752] Buffer I/O error on device sda3, logical block 262771
[74970.484753] Buffer I/O error on device sda3, logical block 262772
[74970.484766] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 393850)
[74970.484767] Buffer I/O error on device sda3, logical block 262775
[74970.484768] Buffer I/O error on device sda3, logical block 262776
[74970.484769] Buffer I/O error on device sda3, logical block 262777
[74970.484781] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 393854)
[74970.484782] Buffer I/O error on device sda3, logical block 262779
[74970.484794] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 393860)
[74970.484808] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 394437)
[74970.484822] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 394440)
[74970.484834] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 394453)
[74970.484845] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 394830)
[74970.484857] EXT4-fs warning (device sda3): ext4_end_bio:323: I/O error 10 writing to inode 13 (offset 0 size 0 starting block 394837)
[74970.487352] print_req_error: I/O error, dev loop2, sector 0
https://bugzilla.kernel.org/show_bug.cgi?id=201685#c174
Change Kernel and check whether errors are still present.
Additional there are really a lot of libevent and device/input/event error messages