OK. Let's start at the beginning.
I have gotten my hands on Asus EEE Pad Transformer TF101. Just the tablet. No dock/keyboard. It was really cheap. I was told it came form USA, and I'm in Europe. I have no warranty, and even if I did, it would've been over the warranty period by now, so RMA is not an option.
It's obviously rooted, has a custom rom and recovery (ClockworkMod Recovery v188.8.131.52. roach2010-tf101-r1)
This is what it says in Settings > About:
Transformer TF101G (although I think it is actually just a Wi-Fi model - TF101, it has no SIM slot - and this means that it probably has wrong ROM flashed, which might be causing the USB problem)
Mobile Dock version:
It seems to be working fine, except for being totally filled up with apps, bloatware and data. Natural instinct was to install a clean ROM. I wanted to go with CM, and a newer Recovery, but I got stuck on the first step. I can't get it recognized on any of my computers. Both Windows 7 and 8.
However, when I plug it in, I get; USB device not recognized. One of the USB devices attached to you computer has malfunctioned... This happens when I connect the USB cable when Android is booted up, when in recovery and also in APX mode, providing I have entered it (I'm not really sure because the display is always black).
In Device Manager, I can see only one exclamation icon (I did enable show hidden devices) in Universal Serious Bus Controllers called Unknown Device, which seems to be from the TF101. I tried uninstalling it. Restarting both the tablet and the computers. I tried to manually override those Unknown Device drivers with ASUS Android USB drivers for Windows and Universal_Naked_Driver_0.72 and ventana apx driver, but it wouldn't take any of them. I also tried installing them manually by right clicking on the INF files, and still nothing.
Then I thought I could mount the sdcard or USB mode in recovery, but that wouldn't work either, since the current recovery doesn't seem to support mounting either the internal memory nor the sdcard.
So now I am stuck. I know I can transfer files by other means, but I need to flash other ROM. Either Stock or Custom. How can I do that without the USB?