Problem with USB keyboard + ehci.mod

[Richard Foltyn]

Dear listers,

I have a USB hub/switch (ATEN US224) to share a USB keyboard / mouse
between two computers.

On one of these computers, the keyboard in the grub2 menu works only
if I pre-load ehci.mod (independent of whether "legacy USB support" is
enabled in BIOS or not).

However, as soon as I load ehci.mod, the partitions present on the
hard drive are no longer seen by grub2's ls and I can no longer boot
into Windows (Linux still works since it resides on LVM).
I.e., BEFORE loading ehci, ls on the grub2 command line shows something like
(hd0) (hd0,msdos1) (hd0,msdos2)  + some LVM volumes

AFTER I load ehci I see
(usb0a) (usb0b) (usb0c) (usb0d) + some LVM volumes

I assume these correspond the x-in-1 card reader that's connected via USB.

Hence I can no longer boot into Windows, which resides on (hd0,msdos1).

If there is no other way to get the keyboard working without loading
ehci, how do I get the disk partitions 'back'?

Any help is greatly appreciated.
Best,
Richard

System info: Ubuntu 14.04 64bit with grub 2.02-beta9;
This is an older BIOS-based system (no UEFI).

lspci | grep -i usb
00:12.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI]
SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:12.1 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0
USB OHCI1 Controller
00:12.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI]
SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:13.0 USB controller: Advanced Micro Devices, Inc. [AMD/ATI]
SB7x0/SB8x0/SB9x0 USB OHCI0 Controller
00:13.1 USB controller: Advanced Micro Devices, Inc. [AMD/ATI] SB7x0
USB OHCI1 Controller
00:13.2 USB controller: Advanced Micro Devices, Inc. [AMD/ATI]
SB7x0/SB8x0/SB9x0 USB EHCI Controller
00:14.5 USB controller: Advanced Micro Devices, Inc. [AMD/ATI]
SB7x0/SB8x0/SB9x0 USB OHCI2 Controller

Hard drive:
Model: ATA Samsung SSD 840 (scsi)
Disk /dev/sda: 250GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End    Size    Type     File system  Flags
 1      1049kB  157GB  157GB   primary  ntfs         boot
 2      157GB   250GB  92,8GB  primary               lvm