I seem to have some bug in "Pool of Radiance".

I'm more than halfway through the game and now one of my characters (Halfling Thief) cannot move during battle. The option just isn't there any more.
On the View screen his movement is 12 and his status is Okay.
On the Encamp, Magic, Display menu he has <No Spell Effects>.

I believe it began during some random battle with some monster that had a "Hold Person" power. He became immobile during the battle and I noticed that he remained so even after. This had happened to me before with other characters, as the effect seems to take a bit of time to recover from, so initially I ignored it and continued playing. But since then many rest periods and game days have gone by and he doesn't seem to recover and I don't really want to return to an earlier save and replay the regions I have already gone through. He is not entirely useless as he has a sling and can melee attack (with Aim Manual) when enemies reach him, but it's still annoying.

I tried casting "Hold Person" on him during a battle, hoping the permanent immobility will disappear with the transient one, but it didn't help.

I should be able to finish the game this way, but anyone has an idea how to solve it?

How much is the little bugger carrying and how high is his maximum carry capacity?

Encumbrance is 320, Movement is 12, Strength is 15.
How do I know his maximum carry capacity?

I have another character with Strength 15, Encumbrance 860, Movement 9, who has no problem moving.

I'll give it a try tonight. Thanks.

The strength table should be in the manual somewhere. But with those numbers that shouldn't be an issue iirc.

If the export/import character trick doesn't work, I would guess there's some item messing up his ability to move.

Let me guess...an Ankheg did it?
Seems to be a bug with them.
If Dispel Magic doesn't work, try every cure in the nearest Temple.
Failing that it's possible the Gold Box Companion - http://personal.inet.fi/koti/jhirvonen/gbc/ - may help.

I'm pretty sure you're right.

In addition to the things I had tried before (mentioned in OP), I now tried:
1) Dispel magic: didn't work
2) Drop all items: didn't work
3) Every cure at a temple: didn't work
4) Remove from party and add back to party: didn't work

So I was left with only the last resort option, which obviously worked, namely remove from party in an earlier save (when he could still move) and add back to party in the current save (after dropping the immobile one). I had hoped to avoid this so as not to lose the EXP, since this same character had been the one that had served as cannon fodder in battles with Spectres/Vampire and had already lost ~30K EXP (after Restoration). Anyhow, the add/remove trick cost him another ~7K EXP. So, while the other single-class characters are at ~79K, he is now at ~43K. Still, it's nice to be able to stretch one's thief's legs again. Off to the pyramid we go.

I refrained from employing a character editor. I don't like using them.

Thanks for the suggestions, everyone. + 1 all around.

In Pool of Radiance, special effects are saved to *.SPC files so for example the third character in save slot A would have them in a file named CHRDATA3.SPC. In the file there are probably counters for certain effects and some bug prevents the effect to be cancelled after a period of time.

Deleting that file from the immobile character might have fixed this. Or copying the file from a "clean" character with no effects. If you still have the save slot you could try this to help future cases.

Good idea. I'll try it tonight and report.

It seems you were perfectly right.

What I did:
0) I made a copy of the entire POOLRAD directory for backup, just in case
1) I used two saves, F (thief immobile) and G (thief mobile).
2) I used their respective SPC files: CHRDATF3.SPC and CHRDATG3.SPC [3 because my thief is third in the roster].
3) I deleted CHRDATF3.SPC.
4) I made a copy of CHRDATG3.SPC and renamed it CHRDATF3.SPC.
5) I launched the game and loaded save F.
6) And suddenly my thief could walk.
7) A miracle.

Just FYI, I compared the files before the operation:
- CHRDATF3.SPC was 27 bytes and CHRDATG3.SPC was 18 bytes.
- Of these, 16 bytes were identical, 2 were different, and 9 were added somewhere in the middle of the F file.

Thank you. Sorry I can't mark you as a solution too, but I can still +1 you.

sorry to Necro this thread, but I seem to have this issue in my game where I have a Half-Elf Fighter Cleric that can't move. He can still attack, his movement on the character sheet says "9", he is not overloaded due to encumbrance or anything. I tried the trick listed above, but it didn't work... Deleted the CHRDATA3.SAV file, made a copy of CHRDATB3.SAV, renamed to CHRDATA3.SAV and reloaded save game A...still couldn't move in combat. I verified save game B character can move, but can't seem to get this to work. Any other ideas?

Try joonashgog's suggestion of deleting (or at least renaming out of the way) the .SPC file. (According to the most recent post prior to yours, it apparently did fix the problem in testing.)

(One flaw with this forum is that only one post can be marked as a solution, and there is no way to change which post is marked if somebody later posts a better solution.)

I was able to get it working, but just copying the SPC file didn't do it. There were three character files, when I copied/renamed all 3 from another save over to the broken save the issue was resolved. Thanks!