I have owned a Bluetooth mouse (Logitech) for about a year. During this time, it has worked flawlessly (and I love it!).

I recently purchased an Apple Wireless Keyboard. Since getting the keyboard, my mouse now lags occasionally. At first I thought that Bluetooth simply did not have enough capacity to handle data from the keyboard and mouse together - but this lag happens very sporadically even when the keyboard is not in use.

Is there something conflicting which causes this lag (software?) ?

Unfortunately- the Apple mice and bluetooth KB's suck monkey balls. It is just the way it is unfortunately... some people have no issues- others want to throw them in the bin.

usual things - check battery status, replace if low.
re-pair devices. monitor situation

I have been running both since the aluminium bluetooth keyboard came out.
I love 'em no lag whatsoever until last week.
Changed batteries didn't help.

Turned out that my old ipod nano, which is busted and can't be seen by my PB but still has music I like and can be charged off the USB, was the problem.

Once I unplugged the nano everything was fine again.

I have a BT Mighty Mouse and a BT Apple Keyboard which work fine. My Mighty Mouse only lags when my phone is transferring data to/from it via Bluetooth, which is understandable.

Ricky.