I am using the same default N97 Task Manager you are, buy holding down the Menu key...
I do, however, also have an app called DeviceInfo which tells me everything about the phone, including:
- C: drive memory available/used
- E: drive memory available/used
- F: drive memory available/used
- RAM available/used
- Batery available/used
- WLAN Mac address
- Phone model
- Firmware version
- Produc type
- Bluetooth status
- Vibraion status
- Auto lock status
- Screensaver timeout
At the mo, it is showing I have around 38MB of RAM free...
Depending on what I am running, I reguarly get down as low as 8-9MB of RAM free....but may be even less as a times apps running in the background will crash/close.
DeviceInfo is available free, found here