I have a fairly old E-Machines AMD 3200+ Sempron based laptop with 185MB of RAM and 40GB HDD, it uses 25 MB of that memory for the on-board video & audio.
Until recently I was running Slax on it but decided to give Lubuntu 10.04 a try.
The Live CD was perfect so I tried to install it.
Initially it completely hung the machine on reboot on installation.
I then did a minimal install using the Ubuntu mini ISO, followed by an ethernet install of the Lubuntu desktop.
This worked fine except when rebooting when it took 2 hours!
I now find everything works beautifully except when I do anything such as changing screen resolution or installing some (but not all) system software. For instance I downgraded WICD to version 1.6 due to the (well documented) WPA2 password issue.
In those cases a reboot, or even straight shut down and restart results in 60-90 minute boot time and it is then really sluggish when it starts.
A straight reboot afterwards starts in normal time and everything is back to normal again.
By the way, between the failed first installation and successful 2nd one I tried Xubuntu using both 8.10 and 10.04 iso Live CDs and a 10.04 alternate CD and they all suffered this 90-120 minute boot problem. They were too slow when operating though.
In many cases (but not always) manually forcing a shutdown with the standby button about 15 minutes in to the restart seems to override the problem.
Anyone else had this problem or got any ideas?

60-90 minutes to boot? That system's got major problems. Have you tried a real ligtweight distro like Puppy, DSL, or TinyCore?

Yes, other non-ubuntu based distros are no problem.
The last I tried was Slitaz 3.0 which is brilliant.
It's nearly an instant boot, the only problem with it was I couldn't find a music player I like, (I prefer Amarok 1.4) and it wouldn't mount and see my DVDs.
I agree the system has a problem, but I must re-iterate the long boot times are only when installing the system or changing screen resolution and when installing some (but not all) software with Synaptic.
It normally boots up in about 15-20 seconds which is fine.
It seems to be some sort of O/S - Hardware conflict, but I have no idea how to identify the problem.
I will add that it was originally purchased with Windows Xp installed and that used to take a painful 12 minutes to boot which is what originally prompted me to switch to Linux (Slax) about 18 months ago.
Slax was fine apart from the need to manually log in and then manually run the startx command every time.
Also the Slax module system of software installation was bit limited although Amarok 1.4 and Kaffeine worked fine, I prefer to use Synaptic.
It wouldn't see my mp3 player if I had the additional SD card in it though, not a problem with Lubuntu or Xubuntu.